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Volume 10,2000 British Columbia Birds Page 1

CONTENTS

GUIDELINES FOR AUTHORS 2

AN APPARENT HYBRID VIOLET-GREEN SWALLOW (TACHYCINETA THALASSINA) X CLIFF SWALLOW(PETROCHELIDON PYRRHONOTA) IN SAANlCHTON, BRITISH COLUMBIABruce Whittington. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16

BUFFLEHEAD (BUCEPHALA ALBEOLA) APPARENTLY CAUGHT BY HARBOUR SEAL (PHOCAVITULINA)

BOOK REVIEWS:

LOONS, by Robert H. BuschReviewed by Martin K. McNicholl 20

THE FEDERATION OF ALBERTA NATURALISTS FIELD GUIDE TO ALBERTA BIRDS,by W. Bruce McGillivray and Glen P. SemenchuckReviewed by Allen N. Wiseley 20

BIRDS AT YOUR FEEDER: A GUIDE TO FEEDING HABITS, BEHAVIOR, DISTRIBUTION ANDABUNDANCE,by Erica H. DlUU1and Diane Tassaglia-HymesReviewed by Bruce Whittington 23

VANCOUVER BIRDS IN 1995, by Kyle Elliott and Wayne Gardner.Reviewed by John M. Cooper 24

SCATS AND TRACKS OF THE ROCKY MOUNTAINS, by James. C. HalfpennyReviewed by Mary J. Taitt 25

THE SIBLEY GUIDE TO BIRDS, by David Allen SibleyReviewed by Tony Greenfield 26

BIRDS OF THE GARRY OAK HABITAT IN BRITISH COLUMBIAWayne R. Erickson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

NORTHERN FLICKER INCUBATES HOODED MERGANSER EGGKaren L. Wiebe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13

JoAnn MacKenzie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

ACKNOWLEDGEMENTS AND EDITOR'S COMMENTS 28


BIRDS O F THE GARRY OAK HABITAT LN BRITISH COLUMBIA

Wayne R. Erickson Forest Practices Branch B.C. Ministry of Forests

Box 95 13, STN PROV GOVT (1450 Government Street) Victoria, B.C. V9C 5Y3

Abstract - In this paper, I characterize the common spring to summer avifauna associated with Garry oak (Quercus gartyanu) in British Columbia, compare it to other habitats, and discuss variation between two study years.

Kq words: avifauna, Garry oak habitat, Gulf Islands, inter-year variation, Vancouver Island.

In 1993 and 1994, I conducted a field survey of the birds of Gany oak (Quercus garryana) habitat as an addition to the main topic of my M. Sc. thesis, which was on Garry oak ecology (Erickson 1996, 1997). Gany oak habitat is both interesting and unique within Canada. It is related biogeographically to habitats in California, occurring on the Gulf Islands and southeastern Vancouver Island, an area with a distinctive meditenanean climate @wards 1993). This range of Gany oak experiences a strong rain-shadow in the lee of the Olympic and Vancouver Island mountains. The result is low precipitation, high sunshine hours and summer drought. These factors combine to set the scene for a mosaic landscape: parklands with spring forb meadows and oak clumps, mossy bluffs often with shrub oaks, open grassy savannahs, and woodlands, sometimes mixed with Douglas-fir (Pseudotsuga rnenziesii). As well as being diverse and productive for plant growth, the area is attractive for human habitation and agricultural development, resulting in ongoing habitat loss and consequent endangerment of the Garry oak ecosystem (Erickson 1993). These pressures compel scientists and environmentalists to expand and share knowledge of the elements of the Gany oak ecosystem, including its birds.

STUDY AREA AND METHODS

My study area extended from East Sooke and Gonzales Hill to Courtenay on Vancouver Island and from East Point, Saturna Island, north to Helliwell Point, Homby Island on the Gulf Islands (Figure 1). While sampling 286 ecological plots over 120 Garry oak locations, I recorded the presence of bird species, identified primarily by ear. Most sites were near sea level, but a number of hillsides were as high as 550 m. Plots were mostly square, ranging in size from about 100 m.2 to about 400 m.2, with a mean size of approximately 225 m.' (Erickson 1996). I visited each plot once over the two year period and was on each plot for approximately 1'; hours. Each species was listed as occurring on each plot in which it was identified. Sampling was between mid- April and early July, a period spanning spring migratory influx, spring vegetation growth, territory establishment, nesting, summer plant growth cessation and the beginning of post-nesting bird dispersal. Since the primary focus of the plot visits was vegetative sampling, bird counts

were done throughout the day, generally excluding the more early morning and late evening periods in which such counts are usually conducted. Sampling was centred on the Saanich Peninsula in the southern part of the area, with sampling trips east, west and north each year as the season progressed (Erickson 1996: Appendix 3). Plot effort was generally equivalent between the years and across the geographical areas within the years, with the exception of the northern Gulf Islands, where little Gany oak habitat was available.

Helliwell Point ... ..La . - --- 7-., ---we ..

ales Hill

-------wetoria

Notn: 1 lo I0 plofs per circle. Note latml m q diaorlion. Kist Soak

Figure I: Garry oakstudy area and plot locations.

The statistical analysis consisted of calculations of fi-equency of each species for each year and the total for both years. Percent frequency is the number of plots in which a species was detected divided by the total number of plots and multiplied by 100. I also tested the adequacy of the data with species/accumulation curves. This analysis subsamples to develop curves which can be used to determine an appropriate number of plots.

Species and group trends were compared for wintering grounds and food sources (Ehdich et al. 1988; Peterson 1990) for species with a greater value than 10% in either year.

NKD

Rectangle

British Columbia Birds Volume 10,2000

TABLE 1 SUMMARY OF GARRY OAK BIRDS IN ORDER OF DESCENDING FREQUENCY

' % fkq = percent kquency: the number of plots in which a species was detected divided by the total number of plots, times 100.

WaVi = Warbling Vireo (Vireogilvus).

' YeWa = Yellow Warbler (Dendroicapelechia).

GCKi = Goldencrowned Kinglet (Regulus satrap).

SwTn = Swainson's Thrush (CuLharur rcshrlalus).

26 27 28

29

30

(Tachycineta tMmsina) European Starling Brown-headed Cowbird Brown Creeper (Certhia americana) Red-breasted Nuthatch (Sit fa canadensis) Bushtit (Psaltriparus minimus)

EuSt BHCo BrCr

RBNu

Bush

5 5 5

5

4

YeWa3 BHCo GCKiJ

ToWa

EuSt

3 3 3

3

2

RBNu BHCo SwTh5

CaVi

WeTa

7 7 7

6

6


RESULTS Varia tiou in Bird Frequency

I documented a total of 1243 occurrences of 66 bud species on the plots over the two years. An additional 12 species were recorded as out of plot, out of habitat or overhead. With 15 1 plots sampled in 1993 and 135 plots in 1994, sampling appears to have been adequate, as judged by the species/accumulation curve tests. A level characterizing about half of the species was obtained with about 15 plots in both years. After 15 plots there was a gradual increase in numbers of species. About 75% of the species were covered by the 45-plot level, leaving only very low-fi-equency species to be covered by additional samples.

The bird species attaining the 30 top fiequency scores are listed in Table 1. An average ofabout four species (4.3) were detected per plot. Three species led in frequency: Orange-crowned Warbler (Vermivora celata) (36.0%), American Robin (TUT~UT migraorius) (35.7%) and Spotted Towhee (Pipilo maculatus) (30.4%) (Table 1; Figures 2,3). The common birds of the Gany oak habitat total 17 species with a fiequency greater than 10%. Collectively they include birds of canopy, of sun-loving shrubs and of openings. The habitat relations of the three leading species suggest the composite nature of the Garry oak habitat.

Figure 2: The ten most frequent Garry oak species.

I Species (see Table 1) I Figure 3:

The 11th to 20th most frequent Garry oak species.

Buds were detected more frequently in 1994 than in 1993. The average number of species detected per plot was considerably higher in 1994 (5.0) than in 1993 (3.7). A linear trendline across the sequential data shows an increase from about 3.6 bird species per plot at the start of the 1993 sampling to about 5.8 per plot at the end of the 1994 season. However, there is wide variation in the numbers, so the trendline has a weak correlation (? = 0.05) with the data.

The no st frequent species changed theu order between the two years (Table 1). Orange-crowned Warbler moved from #2 in 1993 up to #I in 1994. Similarly, the #4, #5 and #6 ianked species, Chestnut-backed Chickadee (Poecile rufacens) (22%), White-crowned Sparrow (Zonotrichia leucophrys) (2 1%) and American Goldfinch (Carduelis tvistis) (20%) increased substantially in 1994. In 1994, 19 species had a fiequency greater than 20%, compared with 11 in 1993; and 19 species had a fiequency >/= 10% coinpared to 12 in 1993.

TABLE 2

CHANGES IN CARRY OAK BIRD FREQUENCY IN 1994

OVER 1993

SPECIES I %CHANGE* ( TYPEOFFQOD I

I Rufous I 236 1 nectar, sap, insects I

Pine Siskin 3 19 ( seeds, insects

I W h i t e - c r o w n e d I 11 1 ( insects, seeds, berries 1

American Goldfinch I 29 1 1 seeds, insects

Hummingbird Chestnut-backed Chickadee

I I I invertebrates I

124

Sparrow Townsend's Warbler House Wren

I S~otted Towhee I 66 1 insects. seeds. h i t I

insects, seeds

I Northwestern Crow 1 59 1 omnivore I

101 86

( Purple Finch 1 52 1 seeds, insects, h i t I

insects i n s e c t s , o t h e r

I Flvcatcher I I 1

Song Sparrow Chipping Sparrow O l i v e - s i d e d

I Orange-crowned ( 10 1 insects, fi-uit, nectar (

47 42 25

insects, seeds insects, seeds insects

Warbler - Northern Flicker P a c i f i c - s l o p e Flycatcher American Robin

1 Warbler I I I

-2 -1 1

Dark-eyed Junco Y e l l o w - r u m p e d

* % change is an increase unless designated with a minus (-) sign.

insects insects

-12

Species (see Table 1) I

insects, h i t -37 -42

seeds, insects insects, berries


Of those with >I= 10% in 1994,12 species were recorded substantially more often than in 1993; six were recorded as kequently or slightly less often, and two species substantially less often (Table 2). Species with the greatest increase in detections include Pine Siskin (Carduelis pinus) (>300%), American Goldfinch and Rufous Hummingbird (Selasphorus mjfis) (>200%) and White-crowned Sparrow and Townsend's Warbler (Dendroica townsend) (> 100%). Declines in detections were more modest with Dark-eyed Junco (Junco hymalis) (-36%) and Yellow-rumped Warbler (Dendroica coronata) (-42%) the only two of a magnitude judged to be reliable. ,

A comparison of these trends shows the largest increase for 1994 over 1993 in seed eaters with insects as a secondary food (+157%) (Table 3). Three of four species were recorded in larger numbers. Species wintering south to Mexico exhibited the next greatest positive change between the two years (+147%), with seven of eight species showing this trend All species of insect eaters that secondarily use seeds were observed more hquently in the second year, averaging 77.7%. Winter residents exhibited an overall positive change (+37%), but three of these species were observed less often. Smaller increases, totalling 20%, were recorded for insect eaters without seeds as supplementary food. Included here were eight species which were split evenly between increased and decreased counts. Species wintering south to Central and South America decreased very slightly in counted birds (-2%) between the two years. The largest combined increase in birds counted is for seedeaters wintering south to Mexico.

DISCUSSION

The habitat relations of the three leading species suggest the composite nature of the Gany oak habitat. Orange-crowned Warblers glean in tree and shrub foliage, American Robins feed on the ground in openings, and Spotted Towhees skulk in thickets. All these elements are important in Gany oak habitat, which is best characterized as a parkland physiognomic type, but varies to hll-canopy woodlands and shrub thickets (Erickson 1996).

Comparison with the Birds of Other Habitats

Most of the top ranking species in my study use Gany oak woodlands in Oregon and black oak (Quercus velutina) habitat in northern California as primary habitat (Anderson 1980; Dedon et al. 1984; Gumtow-Farrier and Gumtow-Farrier 1994). In Oregon, Chestnut- backed Chickadee was associated with Douglas-fir, but Black-capped Chickadee (Poecile atricapillus) (not found regularly on Vancouver Island) used the oak woodland (Anderson 1980). American Robin (#2 ranking in the B.C. oak woodlands) was among the most abundant breeding buds in blue oak (Quercus douglasil) woodland in northern Califomia (Wilson et al. 1991). Species frequent or abundant in California oak woodlands (blue oak, coast live oak (Q, agrifolia)) include Bewick's Wren (Thryomanes bewickii) (#I4 in my study),

Yellow-rumped Warbler (#IS), Spotted Towhee, Dark-eyed Junco (#9), House Wren (Troglodytes aedon) (#lo), Northern Flicker (Colaptes awatus) (#8) and Orange-crowned Warbler (#I) (Vemer 1980; Block and Momson 1991; Tietje et al. 1997). Olive-sided Flycatcher (Contopus cooperi)(#13) is thought to prefer coniferous forests (Verner 1980) and is not mentioned in these California oak studies. However, it is primarily a bud of "edge" habitats and recently bumed areas (Bent 1942; Campbell et al. 1997; Altman and Sallabanks 2000). These are two characteristics of Gany oak habitat, which has much edge associated with the parkland physiognomic type, and several recent hilltop bums.

Spotted Towhee was the most kequent bud species in Gambel oak (Quercusgambeli) habitat of northern California; American Robin and Yellow-rumped Warbler were among the most kequent in southern Arizona. Also listed for Gambel oak are Dark-eyed Junco, Pine Siskin (# 12 in my study), American Goldfinch (#6), White-crowned Sparrow (#5), Orange-crowned Warbler, Northern Flicker, Chipping Sparrow (Spizellapasserina) (# 1 1 )and Cedar Waxwing (Bombycilla ceaF0ru.m) (#17) (Leidolf et al. 2000).

Within B.C., Gany oak can be compared to Douglas-fir, physiognomically similar aspen (Populus tremuloides) parkland and urban habitats. In a local survey of Douglas-fuloak woodlands at Rocky Point, west of Victoria, nine frequent species (> 80% frequency level in those data) were shared with the present study, nine were different, and ten important species (including the #1 and #3 ranking in my study) were lacking (MacLeod undated).

The importance of Chestnut-backed Chickadee was also apparent in Douglas- fir habitat in Washington and Oregon. Along with Pacifio slope Flycatcher (Empidom diflcilis), this species was the most widespread and abundant bud (Anderson 1980; Huff and Raley 1991). Other species in these studies include Northern Flicker, Olive-sided Flycatcher, House Wren (Troglodytes aedon), American Robin, Orange-crowned Warbler, Yellow-rumped Warbler, Chipping Sparrow, Song Sparrow (Melospiza melodia), Purple Finch (Carpodacuspwpureus) and Pine Siskin. However, the importance of these species in Douglas-fir habitat is less that in oak habitat.

American Robin and Northwestern Crow ( C o w cawinus) (#15 in my study) are characteristic suburban species and also Gany oak birds. However, the remaining Gany oak species are more typical of wild habitats. Noticeably lacking &om the top 20 are the suburban1 agricultural species - Anna's Hummingbird (Calypte anna), European Starling (Stwnus vulgaris), Brown-headed Cowbird (Molothrus ater), House Finch (Carpodacus mexicanus) and House Sparrow (Passer domesticus).

In aspen stands of northwest central B.C., American Robin, Cedar Waxwing, Orange-crowned Warbler, Yellow-rumped Warbler and


TABLE 3 COMPARISON OF FACTORS POTENTLALLY INFLUENCING CHANGES IN GARRY OAK

BIRD FREQUENCY BETWEEN 1993 A N D 1994

SPECIES I %CHANGE* I WINTERING AREA I TYPE OF FOOD Wintering residents: u

Chestnut-backed Chickadee I 124 1 resident ( insects, seeds Spotted Towhee I 66 1 resident I insects, seeds, h i t

I ~ o t d % change I 37 I I I

Northwestern Crow Purple Finch Song Sparrow Northern Flicker American Robin Dark-eved Junco

Wintering south to Mexico: P i e Siskin I 3 19 ) to n. Mexico I seeds, insects American Goldfinch 29 1 1 to n. Mexico I seeds, insects

59 52 47 -2

-12 -37

-- - - - - - - - -

wintering to central and South America: Orangecrowned Warbler I 10 1 s. to Guatemala I insects, fruit, nectar Olive-sided Flvcatcher 25 1 montane South 1 insects

White-crowned Sparrow House Wren Chipping Sparrow Rufous Hummingbird Townsend's Warbler Pacific-slope Flycatcher Total % change

I Yellow-rumned Warbler I -42 1 s. to Central America I insects. berries 1

resident resident resident resident resident resident

I Total % c h m e I -2 1 I I

omnivore seeds, insects, fruit insects, seeds insects insects, h i t s seeds. insects

1 1 1 86 42

236 10 1 -1 1 147

Type of food: ~niscellaneous foods:

to cenh-al Mexico s. through Mexico '

s. through Mexico n. Mexico Mexican high-lands to Costa Rica Mexico

Type of food: seeds primary:

insects, seeds, berries insects, other invertebrates insects, seeds nectar, sap, insects insects insects

seeds, insccts, fiuit seeds, insects seeds, insects seeds, insects

Purple Finch Pine Siskin American Godfich Dark-eyed Junco Total % change

Northwestern Crow I 59 ( resident I omnivore Ru fous Hummingbird 236 1 n. Mexico to Costa Rica I nectar, sap, insects

Type of food: insects primary, seeds secondary:

d . . - House Wren I 86 1 s, through Mexico I insects, other invertebrates Orange-crowned Warbler 10 1 s. to Guatemala ( insects, fruit, nectar

Song Sparrow Chipping Sparrow Total % change

52 3 19 29 1 -37 157

insects, seeds, h i t insects, seeds, berries insects, seeds

Spotted Towhee White-crowned Sparrow Chestnut-backed Chickadee

Northern Flicker I -2 ( resident 1 insects I

resident n. to Mexico n. to Mexico resident

Tvne of food: insects nrimarv. without seeds as secondarv:

47 42 78

American Robin Yellow-rumped Warbler Townsend's Warbler Olive-sided Flycatcher

Pacific-slope Flycatcher I -1 1 ( Mexico I insects Total % change 20 1 * % change is an increase unless designated ~'it11 a nliuus (-) sign.

66 1 11 124

resident to Central Mexico resident resident s. bough Mexico

- -

-12 -42 10 1 25

insects, seeds insects, seeds

resident s. to South America Mexican high-lands to Costa Rica montane South America

insects, fiuit insects, berries insects insects


Dark-eyed Junco were found regularly in mature and old aspen, while Purple Finch (#I9 in my study) was less frequent (Pojar 1995). Pine Siskin was found in mixed aspen-conifer (spruce, Lodgepole pine (Pinus contorta)). White-crowned Sparrow, Chipping Sparrow (# 1 1) and Rufous Hummingbird (# 16) were on clearcuts.

Weather

Weather in the study years may have influenced the numbers of buds observed. There had been low precipitation and warm temperatures leading up to, and continuing for the duration of these years. The exception was growing season precipitation, which was high in 1993 and normal in 1994. The study years were also affected by the El Niiio climatic phenomenon (NOAA 200 1). Two prior years had El Niiio events in both winter and summer. Summer El Niilo events were experienced in 1993 and 1994. El N a o effects vary along the Pacific Coast. Winter conditions are slightly warmer (+0.75' C.) in southwestern B.C. than usual; California is about normal; and the Mexican highlands are colder (0.25' C.). Breeding conditions are slightly warmer here in B.C. Neither winter nor summer precipitation are affected much by the El Niiio cycle here, but winter increases as high as 0.8 mm./day are recorded from California south into Mexico.

Recent research has linked lower survival of Neotropically- wintering songbirds with the effects of reduced rainfall during El Niiio years (Sillett et al. 2000). Possible mechanisms include scarcer seed and insect foods, consequent production of fewer young, and elevational dislocation due to warm, dry conditions (Pounds et al. 1999; Sillett et al. 2000).

Several of the species recorded more frequently in 1994 both migrate and remain in B.C. in winter. Their population trends could relate to winter weather or residual seed crops here, to conditions on southern wintering grounds, or to several other factors. Warmer temperatures may have created favourable winter survival conditions for resident species during the El Nifio years of the study time period. During the 199 1 and 1992 winter El Niiio events, species wintering in the Mexican highlands may have experienced increased mortality due to cooler conditions. Populations may have been recovering subsequently during the favourable conditions in the summer 1993 El Niiio. A continuation of this trend could have led to the apparent higher frequencies recorded during the 1994 El Niiio summer.

The same set of conditions and population trends may be mirrored for southwestern B.C.: apparent initial low populations in 1993 followed low precipitation and high growing season temperatures; favourable growing season rainfall in 1993 combined with a subsequent mild winter; and both warm temperatures and adequate moisture continued into the 1994 nesting season. Given these conditions, populations of both residents and migrants may have increased during the study years.

Other Factors

Of the species with the greatest increases in detections, seedeaters, such as Pine Siskin and American Goldfmch, are known for the irruptive nature of their occurrence (Newton 1985). Increases in their numbers in any given area may signify shifts in their distribution. Feeder augmentation or higher rates of flowering may allow more pairs of Rufous Hummingbirds to breed within a specific area (Bowles fide Bent 1940; Calder 1993), resulting in production of more young within those areas.

Other factors, including sampling effects, could influence the outcome by year. The influence and timing of local weather events on the nesting success of each species, predatorlprey dynamics in different seasons, the adaptability of different species to changing conditions, Neotropical habitat degradation and epizootics may warrant hrther investigation.

SUMMARY

The characteristic, common avifauna of Garry oak habitat in B.C. included 17 species with a frequency of greater than 10 percent, led by Orange-crowned Warbler, American Robin and Spotted Towhee, each on approximately one-third of the study sites. Bird frequency and ranking shifted between the two years of the study. The two-year results stress the need to survey the birds of a given habitat for several years.

This community has affinities with related habitats, particularly with other western oak woodlands. There is less similarity to Douglas-fw, urban and aspen woodland habitats in B.C.

An understanding of local population trends should be underscored by continent-wide population dynamics and weather patterns. Many factors influence individual species, groups of species or the entire avifauna. The comparisons I made suggest that the El Nifio cycle may provide a useful framework for interpreting some annual changes in bird frequencies. Its relative importance compared to other influences warrants further study.

Knowledge of the Gamy oak avifauna may stimulate fiuther interest, and promote its inclusion as a component of the conservation efforts so important for this endangered ecosystem.

ACKNOWLEDGEMENTS

I would like to thank Martin K. McNicholl, Andrew C. Stewart and Mary J. Taitt, who corrected my draft and commented generously. The field work for this study was completed in a M. Sc. program at the University of Victoria toward which the B.C. Ministry of Forests approved a part-time education leave. Grants provided by the Canadian Wildlife Service and its employees assisted in the first year of this study.


LITERATURE CITED

Altman, B. and R. Sallabanks. 2000. Olive-sided Flycatcher (Contopus cooperi). No. 502 in A. Poole and F. Gill (Editors). The buds of North America. The Buds of North America, Inc., Philadelphia.

Anderson, S. H. 1980. Habitat selection, succession, and bird community organization. pp. 13-26 in R. M. deGraff (Technical Coordinator). Management of western forests and grasslands for nongame buds. U.S. Department of Agriculture, Forest Service, General Technical Report INT-86.

Bent, A. C. 1940. Life histories of North American cuckoos, goatsuckers, hummingbirds and their allies. US. National Museum Bulletin 176.

Bent, A. C. 1942. Life histories of North American flycatchers, larks, swallows, and their allies. U.S. National Museum Bulletin 179.

Block, W. R. and M. L. Morrison. 1991. Influence of scale on the management of wildlife in California oak woodlands. pp. 96-104 in R. B. Staniford (Technical Coordinator). Proceedings of the symposium on oak woodlands and hardwood rangeland management. U.S. Department of Agriculture, Forest Service, General Technical Report PSW-126.

Calder, W. A. 1993. Rufous Hummingbird Selasphorus rufus. No. 53 in A. Poole and F. Gill (Editors). The birds of North America. Academy ofNatural Sciences, Philadelphia and American Ornithologists' Union, Washington.

Campbell, R. W., N. K. Dawe, I. McTaggart-Cowan, J. M. Cooper, G. W. Kaiser, M. C. E. McNall and G. E. J. Smith. 1997. The buds of British Columbia. Volume 3. University of British Columbia Press, Vancouver.

Dedon, M. F., S. A. Laymon and R. H. Barrett. 1984. Evaluating models of wildlife-habitat relationships of buds in black oak and mixed conifer habitats. pp. 1 15-1 19 in J. Verner, M. L. Morrison and C. J. Ralph (Editors). Wildlife 2000: modelling habitat relationships of terrestrial vertebrates. University of Wisconsin Press, Madison.

Edwards, Y. 1993. Our Nevada desert & California oaklands. B. C. Naturalist 3 1 (4):5-6.

Ehrlich, P. R., D. S. Dobkin and D. Wheaye. 1988. The birder's handbook: a field guide to the natural history of North American buds. Simon and Schuster, Toronto.

Erickson, W. R. 1993. Gany oak ecosystems at risk (brochure). Wildlife Branch, B. C. Ministry of Environment, Lands and Parks, Victoria.

Erickson, W. R. 1996. Classification and interpretation of Gany Oak (Quercus garryana) plant communities and ecosystems in southwestem British Columbia. M. Sc. thesis, University of Victoria, Victoria.

Erickson, W. R. 1997. Gany oak (Quercus garryana) and its ecosystems. B.C. Naturalist 35(3):4-5.

Gumtow-Farrier, D. and C. Gumtow-Farrier. 1994. Wildlife on white oak woodlands (brochure). Woodland, Fish and Wildlife. World Forestry Center, Portland, Oregon.

Huff, M. H. and C. M. Raley. 199 1. Regional patterns of diurnal breeding bird communities in Oregon and Washington. pp. 117-12 1 in L. F. Ruggiero, K. B. Aubry, A. B. Carey and M. H. Huff (Technical Coordinators). Wildlife and vegetation of unmanaged Douglas-fir forests. U.S. Department of Agriculture, Forest Service, General Technical Report RMRS-GTR-48.

Leidolf, A., M. L. Wolfe and R. L. Pendleton. 2000. Bud communities of Gambel oak: a descriptive analysis. US. Department of Agriculture, Forest Service, General Technical Report RMRS-GTR-48.

Newton, I. 1985. Irruption. pp. 307-309 in B. Campbell and E. Lack (Editors). A dictionary of birds. Buteo Books, Vermillion, South Dakota.

Peterson, R. T. 1990. A field guide to western birds. Thud edition. Houghton Mifflin, Boston.

Pojar, R. A. 1995. Breeding bird communities in aspen forests of the Sub-Boreal Spruce (dk Subzone) in the Prince Rupert Forest Region. B.C. Ministry of Forests Land Management Handbook 33, Victoria.

Pounds, J. A., M. P. L. Fogden and J. H. Campbell. 1999. Biological response to climate change on a tropical mountain. Nature 398:611-615.

Sillett, T. S., R. T. Holmes and T. W. Sheny. 2000. Impacts of a global climate cycle on population dynamics of a migratory songbird. Science 288:2040-2042.

Tietje, W. D., J. K. Vreeland, N. R. Siepel and J. L. Docker. 1997. Relative abundance and habitat associations of vertebrates in oak woodlands in coastal-central California. pp. 391- 400 in N. H. Pillsbury, J. Vemer and W. D. Tietje (Technical Coordinators). Proceedings ofa symposium on oak woodlands: ecology, management and urban interface issues. U.S. Department of Agriculture, Forest Service, General Technical Report PS W GTR- 160.

Vemer, J. 1980. Birds of California oak habitats: management implications. pp. 246-264 in T. R. Plumb (Technical Coordinator). Ecology, management, and utilization of


California oaks. U.S. Department of Agriculture, Forest Service General Technical Report PSW GTR-44.

Wilson, R. A., P. Manley and B. R. Noon. 1991. Covariance patterns among birds and vegetation in a California oak woodland. pp. 126-135 in R. B. Staniford (Technical Coordinator). Proceedings of the symposium on oak woodlands and hardwood rangeland management. U.S. Department of Agriculture, Forest Service, General Technical Report PSW GTR-126.

UNPUBLISHED DOCUMENTS CITED

MacLeod, A. undated. Unpublished field notes, Rocky Point bird survey.

NOAA. 2001. National Oceanic and Atmosphere Administration, CDC ENS0 website: www.cdc.noaa.gov.

BIRDS OF THE CARRY OAK HABITAT IN BRITISH COLUMBIA Enlarged view of Figure 1.

Helliwell

Notes: 1 to 10 plots per circle. Note lateral map distortion. \ ~ a s t Sooke

Volume 10,2000 British Columbia Birds Page 13 - - - -

NORTHERN FLICKER INCUBATES HOODED MERGANSER EGG

Karen L. Wiebe Department of Biology

University of Saskatchewan 1 12 Science Place

Saskatoon, Saskatchewan S7N 5E2

Abstract - Misdirected incubation has been reported for a few species of secondary cavity-nesting birds, presumably resulting from intense competition for nest sites. Here I report a case of a Northern Flicker pair, primary cavity excavators, incubating an egg of a Hooded Merganser. The flickers probably suffered a high reproductive cost as a result of this behaviour, as they fledged only two young from their own seven eggs. The Hooded Merganser embryo reached an advanced stage of development, but did not hatch. It is unclear why a woodpecker with the ability to excavate a new nest would incubate a foreign egg and suffer high reproductive failure.

Key worak cavity nesting, Colaptes auratus, competition, incubation, Northern Flicker.

Numerous buds and mammals in forest ecosystems depend on tree cavities for nesting. Primary cavity nesting species, such as many woodpeckers, excavate their own nests which may be used subsequently by a suite of secondary cavity nesters which cannot excavate. The availability of suitable nests appears to limit the population size of some cavity nesters (Newton 1994), so competition for tree holes or nest boxes may be intense (Simpkin and Gubanich 1991). Excluding cases of brood parasitism, reports of misdirected incubation among cavity nesters are rare and seem to have involved secondary cavity nesting birds in most cases: American Kestrel (Falco sparverius) (Sumner 1933; Dawson and Bortolotti 1997), Eastern Screech-Owl (Om mio) (Breen and Panish 1996), and Ash-throated Flycatcher (Myiarchus cinerawem) (Simpkin and Gubanich 1991). Here I report misdirected incubation by a primary cavity excavator, the Northern Flicker (Colaptes awam), and its apparent consequences to reproductive success.

STUDY AREA

I have studied flickers since 1997 at Riske Creek, British Columbia (51' 52' N, 122' 21' W). Each year, about 85 pairs of flickers using natural cavities have been monitored on a 75 lan2 area of mixed forest and grassland. For details of the study area and general methods see Wiebe (2000,2001). Here, as part of a long-term study, colleagues and I have recorded 32 species of birds and 12 of mammals that use cavities. Flickers excavate the majority of nests used by the other species at Riske Creek (see Martin and Eadie 1999).

OBSERVATIONS

On 9 May 2000, I discovered a pair of flickers defending a cavity containing one Hooded Merganser (Lophodytes cucullatus) egg measuring 54.4 mrn. x 44.3 rnm. and resembling the illustration of the egg of this species in Harrison (1984). The nest was checked every second day thereafter, and the first flicker egg appeared one week later, on 16 May. A complete clutch of seven flicker eggs together with the one merganser egg was being incubated by the female flicker on 24 May. As incubation usually begins near clutch completion, and the

eggs are laid one day apart (Wiebe, unpublished data), the flickers probably began incubating on 22 May. The flicker eggs, clustered together on one side of the duck egg, were dwarfed by it. When the nest was visited again on 3 1 May, the male was incubating, with the woodpecker's eggs scattered around the duck egg. The duck egg was warm, but two of the flicker eggs were only at ambient temperature. Eight days later, the nest contained two 3-day old flicker chicks, one newly hatched chick and its eggshell and one dead 1-day old chick (ages estimated fiom body mass measurements). The three unhatched flicker eggs were examined on 1 1 June, when two contained small embryos and one showed no development. The merganser egg was still warm and was left in the nest. By 20 June, the smallest of the three flicker chicks had died, leaving only two, but the merganser egg was still being kept warm by the brooding male flicker. When the two flicker chicks were banded on 26 June, a few days prior to fledging, the duck egg was cold, so was removed and opened. Inside was a merganser embryo almost fully developed with only a small yolk sack, not more than three days &om hatching, according to waterfowl biologists on the study area.

DISCUSSION

Of the previous reports of misdirected incubation, none has involved a greater size difference between eggs than this case, and it seems incredible that flickers would attempt to incubate a duck egg. According to Hoyt's (1979) equation, the average volume of the seven flicker eggs in the nest was 7.18 cm.', while the merganser egg was 52.0 cm.'. tncubating the egg had probably had negative consequences for the pair of flickers, which fledged only two offspring fiom their seven eggs, a much lower success than average (Wiebe and Swift 200 1). Uneven incubation temperatures and the inability to cover eggs may cause extreme hatching asynchrony and development failure (Wiebe and Bortolotti 1993); both problems occurred in this flicker nest.

Given their high reproductive failure, it is unclear why the woodpeckers chose to use the cavity after presumably evicting the Hooded Merganser. Flickers re-use old cavities more often than other


woodpeckers (Ingold 1994) but are capable of excavating a new nest. Suitable decayed aspen trees are numerous on our site, so nest sites probably are not limiting. Both the male and female flicker were two years old (presumably experienced breeders, as yearlings on the study area commonly breed) and their laying date was early in the season, so there should have been time to search for, or excavate, a different cavity. Abnormally large eggs added to the nests of incubating birds may be a "supernormal stimulus" triggering tenacious incubation behaviour (Tinbergen 195 1). However, the duck egg was in the cavity at least two weeks before the flickers began incubating, so the flickers did not succumb to an immediate stimulus to incubate. Flickers often compete with European Starlings (Sturnus vulgark) on our site, but have tossed out foreign starling eggs that appeared in cavities they were attempting to excavate. Lott (1939) reported a flicker feeding a brood of starlings, but it is not known whether or not the woodpeckers incubated the starling eggs. Flickers may evict Tree Swallows (Tachycineta bicolor) (Rendell and Robertson 1989) and American Kestrels (Moore 1995) from nests, but destroy the foreign eggs before initiating their own clutch. Perhaps the duck egg was too large to throw out, but flickers seem to have the morphology to puncture and remove large eggs.

Because the incubation period of flickers is 1 1 days (Moore 1995), while that of Hooded Mergansers is at least 29 days (Ehrlich et al. 1988), the duck egg in this situation would be unlikely to hatch. Still, it receivedabout 28 days of at least irregular incubation and reached an advanced stage of development. A similar case of a Bufflehead (Bucephala albeola) egg incubated by an American Kestrel was reported by Dawson and Bortolotti (1997). In that situation, the duck egg hatched because its incubation period matched closely that of the kestrel. Intense competition may lead occasionally to maladaptive incubation of foreign eggs by cavity-nesters and perhaps nest-sites might be more limiting than previously thought even for excavators, such as woodpeckers.

ACKNOWLEDGEMENTS

These observations were made while conducting research financed by NSERC (National Science And Engineering Research Council). I thank M. Bidwell, C. Elchuck and A. Pantel for tireless help in the field and William S. Moore and Ken H. Morgan for comments on the manuscript. Thanks to Matt Evans for examining the merganser egg and embryo.

LITERATURE CITED

Breen, T. F. and J. W. Parrish, Jr. 1996. Eastern Screech-Owl hatches an American Kestrel. Journal of Field Ornithology 67:6 12- 613.

Dawson, R. D. and G. R. Bortolotti. 1997. Misdirected incubation in American Kestrels: a case of competition for nest sites? Wilson Bulletin 109 :732-734.

Ehrlich, P. R., D. S. Dobkin and D. Wheye. 1988. The birder's handbook. Simon and Schuster, New York.

Harrison, C. 1984. A field guide to the nests, eggs, and nestlings of North American birds. Collins, Toronto.

Hoyt, D. F. 1979. Practical methods of estimating volume and fresh weight of bird eggs. Auk 96:73-77.

Ingold, D. J. 1994. Nest-site characteristics of Red-bellied and Red- headed woodpeckers and Northern Flickers in east central Ohio. Ohio Journal of Science 94:2-7.

Lott, W. M. 1939. Flicker rears starlings. Canadian Field-Naturallist 5359.

Martin, K. and J. M. Eadie. 1999. Nest webs: a community-wide approach to the management and conservation of cavity- nesting forest birds. Forest Ecologv and Management 1 15:243-257.

Moore, W. S. 1995. Northern Flicker Colaptes auratus. No. 166 in A. Poole and F. Gill (Editors). The birds of North America. Academy of Natural Sciences, Philadelphia and American Ornithologists' Union, Washington.

Newton, I. 1994. The role of nest sites in limiting the numbers of hole- nesting birds: a review. Biological Conservation 70:265-276.

Rendell, W. B. and R. J. Robertson. 1989. Nest-site characteristics, reproductive success and cavity availability for Tree Swallows breeding in natural cavities. Condor 9 1975-885.

Simpkin, J. L. and A. A. Gubanich. 199 1. Ash-throated Flycatchers (Myiarchus cinerascens) raise Mountain Bluebird (Sialia currucoides) young. Condor 93 :46 1-462.

Sumner, F. A. 1933. Young Sparrow Hawks and a Screech Owl inthe same nest. Condor 35:23 1-232.

Tinbergen, N. 195 1. The study of instinct. Oxford University Press, New York.


Wiebe, K. L. 2000. Assortative mating by color in a population of hybrid Northern Flickers. Auk 11'7525-529.

Wiebe, K. L. 2001. Microclimate of tree cavity nests: is it important for reproductive success in Northern Flickers? Auk 1 18: 412- 421.

r

Wiebe, I<. L. and G. R. Bortolotti. 1993. Brood patches of American Kest~els: an ecological and evolutionaty perspective. Omk Scandinavica 24: 197-204.

Wiebe, K. L. and T. L. Swift. 2001. Clutch size relative to tree cavity size in Northern Flickers. Journal oflvian Biology 32: 167- 173.


AN APPARENT HYBRID VIOLET-GREEN SWALLOW (TACHYCZNETA TltALASSZNA) X CLWF SWALLOW (PETROCHELIDON PYRRHONOTA) IN SAANICHTON, BRITISH COLUMBIA

Bruce Whittington 347 Millstream M e Road Victoria, B.C. V9B 6H5

Abstract - An oddly-plumaged swallow that visited a nestbox in Saanichton, B.C. appeared to be a hybrid between Violet-green and swallows. This appears to be the fmt probable hybrid between these species described and probably only the second reported case of potc hybridization between Violet-green Swallow and any other species.

Key words: British Columbia, hybridization, swallows.

Violet-green Swallows (Tm&cineta thalassina) nest regularly in nestboxes in residential areas in southwestern British Columbia. In one such location in Saanichton on southern Vancouver Island, this species annually raised young in a nestbox affuted to the gable end of a garage, about three metres above the ground.

On 2 July 2000, two adult Violet-green Swallows were being observed as they brought food to nearly fledged young in the nestbox, when they became alarmed, calling agitatedly. In looking for the cause of their alarm, I noted a different swallow in the area. Ibis bird flew back and forth several times, and then perched on the top of the nestbox. It spent about seven or eight minutes around the nestbox, moving fiom its top to the roof of the garage less than a metre away. It also perched at the opening of the box, and looked inside and at the surroundings, as Violet-green Swallows do when investigating a potential nest site. It did not interact with the juvenile birds in the nestbox. The adult Violet-green Swallows swooped at the intruding swallow several times (see Figure I), and were obviously distressed. After a short time, the odd swallow left and was not seen again.

Figure 1: Adult Violet2reen Swallow attackiug apparent hybrid. Saanichton, B.C. 2 July 2000.

Cliff :ntial

The odd swallow was similar in shape to a Violet-green, but was perhaps slightly larger. The tail was not noticeably forked The upperparts showed some iridescent greenish, but were not as bright as on a male Violet-green, nor as olivaceous as on a female. The sides of the rump were mottled whitish, but it was not possible to determine whether or not this covered the entire rump. The undeiparts were white or nearly so. The head, chin and throat were washed entirely with warm ochrebuff, with a crown patch of iridescent greenish (Figures 2 and 3). There was at least a partial collar of white extending around the nape. The iris was dark brown, and the bill and feet dark. The bird was not heard calling.

The plumage pattern and greenish iridescence suggest a Violet-green x Cliff Swallow (Tachycineta thalawina x Petrochelidonpyrrhonota). It was very similar to; a Violet-green Swallow in its appearance and behaviour at a nest site. The warm buff colouring should eliminate all but Cliff, Barn (Himn& rwtica), and the geographically unlikely Cave (Petrochelidon fitlva) swallows. The behaviour at the nestbox, and unforked tail do not suggest Barn Swallow, whereas the buff forehead and throat suggest that one of the parents was a Cliff Swallow. During a visit to Victoria in November 200 1, field guide author David A. Sibley examined my slides of this bird and agreed that it was probably a Violet-green x Cliff Swallow, although commenting that field marks alone could not eliminate Cave Swallow as a potential parent.

Term (1980) reported single records ofhybrid Cliff x Barn Swallows and Cliff x Tree (Petrochelidon pyrrhonota x Tachycineta bicolor) Swallows. More recently, a shift in habitat use by Cave Swallows has been accompanied by localized hybridization between them and Barn Swallows in Texas culverts (Martin and Selander 1975; Martin 1980), and an extralimital Violet-green Swallow bred with a Tree Swallow in Illinois, apparently without producing young (Johnson and Moskoff 1995). Johnson and Moskoff (1995) also mentioned a report of a female Violet-green Swallow copulating with a male Barn Swallow, but no such observation is mentioned in the source (Gullion 1947) cited by them. No previous reports of hybrids between Cliff and Violet- geen swallows appear to have been published (Brown et al. 1992; Brown and Brown 1995; C. R. Brown personal communication; Pyle 1997).


The visit by this apparent hybrid swallow apparently had no ill effect Gullion, G. W. 1947. Use ofartificial nesting sites by Violet-green and on the survival of the young in this box, as they fledged successfully. Tree swallows. Auk 64:4 1 1 4 15.

ACKNOWLEDGEMENTS Johnson, L. G. and W. Moskoff. 1995. First hybridization attempt between a Violet-green Swallow and Tree Swallow.

David F. Fraser, Martin K. McNicholl and Ken H. Morgan made Meadowlark 4:2-3. helphl comments on an earlier draft of this note. Joann Constantinides of the Josselyn Van Tyne Memorial Librslly of the Wilson Martin, R. F. 1980. Analysis of hybridization between the hirundinid Ornithological Society provided a copy of the Johnson and Moskoff genera Hirundo and Pelrochelidon in Texas. Auk 97:148- reference to M. K. McNicholl. 159.

LITERATURE CITED Martin, R. F. and R. K. Selander. 1975. Morphological and biochemical evidence of hybridization between Cave and Barn swallows. Condor 77:362-364. Brown, C. R. and M. B. Brown. 1995. Hirundo pyrrhonola, Cliff

Swallow. No. 149 in A. Poole and F. Gill (Editors). The birds of North America. The Academy of Natural Sciences, Pyle, P. 1997. Identification guide to North American birds. Part I. Philadelphia and American Ornithologists' Union, Columbidae to Ploceidae. Slate Creek Press, Bolinas, Washington. California.

Brown, C. R., A. M. Knott and E. J. Damrose. 1992. Tachycinera Terres, J. K. 1980. The Audubon Society encyclopedia of North thalmsina, Violet-green Swallow. No. 14 in A. Poole, P . American birds. Alfred A. IOlopf, New York. Stettenheim and F. Gill (Editors). The birds of North America. The Academy of Natural Sciences, Philadelphia and American Ornithologists' Union, Washington.

Figure 2: Apparent bybrid swallow at entrance to nest box. Saanichton, B.C. 2 July 2000.

Figure 3: Apparent hybrid s~vallow on roof of garage, Sannichton, B.C. 2 July 2000


BUFFLEHEAD (BUCEPHALA ALBEOLA) APPARENTLY CAUGHT BY HARBOUR SEAL (PHOCA MTULZNA)

Jo Ann MacKenzie 1543 1-2 1 Avenue

Surrey, B.C. V4A 6A8

Absfract - I document apparent predation on a Bufflehead by a Harbour Seal in Boundary Bay.

Kq words: Bufflehead, Bucephala albeola, Harbour Seal, Phoca vitulina, predation, Boundary Bay, Surrey.

At approximately 1 1 :00 Pacific Standard Time on 1 1 January 2000, while participating in a B.C. Coastal Waterbird Survey at Crescent Beach, Surrey, I noticed a female-plumaged BuMehead (Bucephala albeola) that appeared to be in distress approximately 300 m. offshore in Boundary Bay. Curious, I watched through Zeiss Dialyst 10 x 40 BJGA T binoculars as the bird vigorously flapped its wings, beating the water's surface, moving 2-3 m. in one direction, then another. At the end of these agitated "dashes," it disappeared underwater, as if diving. After the third "dash-dive-resurface" sequence, I saw an adult-sized Harbour Seal (Phoca vitulina), recognized by its brown-blotched, grey " s k i " surface and then dive approximately 2 m. behind and toward the duck, seemingly pursuing it. I wondered why the duck didn't escape by taking flight, inasmuch as Buffleheads normally take off easily ti-om the water, with less effort than other diving ducks (Bent 1925; Palmer 1976; Cramp 1977; Madge and Burn 1988). Although I did not see the seal again, the apparent pursuit continued, with three more "dash-dive- resurface" sequences by the duck. After a fourth "dash" of 1.5 to 2 m., the duck disappeared under water, and did not resurface. The Bufflehead was probably finally eaten by the seal.

DISCUSSION

The shallow waters of Boundary Bay support a moderate population of Harbour Seals, which are often seen in the water, or hauled out on sandbars and banks near the Nikomekl River. The BuMehead is a common wintering species in Boundary Bay, ti-equently observed ti-om Blackie Spit and Crescent Beach. Eight were seen on the survey that day, but none of the others was in the immediate vicinity of the attack.

Adult seals need as much as 10 kg. of food daily (Schliemann 1990). The primary food of the Harbour Seal is fish (Burt and Grossenheider 1964), including anchovy, cod, flounder, hemng, lamprey, rockfish, salmon, smelt and trout (Cowan and Guiguet 1965; Nowak 199 1) and shellfish (Cowan and Guiguet 1965). Their diet also includes octopus (Nowak 199 1) and there have been observations of birdcatching or of bird remains in stomach contents of several northem pinniped species, including Harbour Seals, on the Canadian west coast (Lucas and McLaren 1988).

Maine (French 198 1). Off Eastern Egg Rock, Muscongus Bay, Maine, in August 1975, fish of undetermined species attacked a fledgling Black Guillemot (Cepphus gylle) and two eclipse-plumaged Common Eider drakes (Somateria mollissima). Eventually the eiders escaped, but the guillemot was disabled; a bird believed to be the same guillemot was found beached the next day. The webbing of the feet had been pierced, and both its legs had numerous lacerations that severed the main tendons, paralyzing the legs. In 1974, other seabirds were found similarly injured (French 198 1). At Triple Island, B.C., Killer Whales (Orcinus orca) were seen preying upon ducks, mostly White-winged Scoters (Melanitta fusca) (Odlum 1948). However, with the exception of well-known predation by Leopard Seals (Hydrwga leptonyx) on penguins, birds do not usually form a large part of the diet of pinnipeds (Hamilton 1946).

There is little in the literature regarding predation on BuMeheads. On land, large falcons may prey on them (Bent 1925; Cannings et al. 1987), as do Bald Eagles (Haliaeetus leucocephalus) occasionally (Phillips 1922-1926; Retfalvi 1970; Todd 1979). Munro (1929) found a BuMehead preyed upon by a Snowy Owl (Nyctea scandiaca). Erskine (1972) mentions Great Homed Owl (Bubo virginianus) as a common predator in Bufflehead breeding areas, and perhaps Cooper's Hawk (Accipiter cooperii). In southeastern Alaska, BuMeheads are sometimes preyed upon by mink (Mustela vison) along the edge of the ice (Phillips 1922-1926), and females killed on the nest by weasels (Mustela sp.), mink and Barrow's Goldeneye (Bucephala klandica) (Gauthier 1993). Such references as Delacour (1959), Rodgers (1974), Johnsgard (1975,1978,1979), Bellrose (1976), Palmer(1976), Cramp (1977), and Heintzelman (1978) provide no information on predators of BuMeheads.

A small duck, such as a Bufflehead, is apparently unusual prey for a Harbour Seal. Although the waters off Crescent Beach are too shallow for fishing activities, making entanglement in fishing gear as reported by Burtch (1 923) unlikely, the bird may have been entangled in some other equipment or already injured or disabled in some other way, affording an opportunistic target for the seal.

Some predation on seabirds by Grey Seals (Halichoerus gypus), octopuses (Octopus sp.), sharks (Galeocerdo cuvieri, Carcharodon carcharias, Carcharinus leucas, C. longimanus), monkfish (Squatina squatina) and cod (Gadus macrocephalus) has been documented in


ACKNOWLEDGEMENTS

I thank Anthony J. Erskine and Ken H. Morgan for comments which helped improve the manuscript. I am also p t e h l to Martin K. McNicholl for his interest and encouragement, and for providing some references and fiuther helphl comments.

LITERATURE CITED

Bellrose, F. C. 1976. Ducks, geese and swans of North America. Stackpole Books, Harrisburg, Pennsylvania.

Bent, A. C. 1925. Life histories of North American wild fowl. Part 11. U. S. National Museum Bulletin 130.

Bwt, W. H. and R P. Grossenheider. 1964. A field guide to the mammals. Second edition. Houghton Mifflin, Boston.

Burtch, V. 1923. Some notes on the birds of the Branchport,N.Y., region in 1922. Auk 40649-652.

Cannings, R. A., R. J. Cannings and S. G. Cannings. 1987. Birds of the Okanagan Valley, British Columbia Royal British Columbia Museum, Victoria.

Cowan, I. M. and C. J. Guiguet. 1965. The mammals of British Columbia. British Columbia Provincial Museum Handbook No. 1 1, Victoria.

Cramp, S. (Editor). 1977. Handbook of the birds of Europe [,I the Middle East and North Africa. The birds of the western Palearctic. Volume 1. Oxford University Press, Oxford.

Delacour, J. 1959. The waterfowl of the World. Volume 3. Country Life, London.

Erskine, A. J. 1972. Buffleheads. Canadian wildlife Service Monograph Series 4.

French, T. W. 1981. Fish attack on Black Guillemot and Common Eider in Maine. Wikion Bulletin 93 :279-28 1.

Gauthier, G. 1993. Bumehead Bucephala albeola Number 67 in A. Poole and F. Gill (Editors). The birds of North America. Academy of Natural Sciences, Philadelphia and American Ornithologists' Union, Washington.

Hamilton, J. E. 1946. Seals preying on birds. Ibis 88:131-132.

Heintzelman, D. S. 1978. North American ducks, geese & swans. Winchester Press, New York.

Johnsgard, P. A. 1975. Waterfowl of North America. Indiana University Press, Bloomington, Indiana.

Johnsgard, P. A. 1978. Ducks, geese and swans of the World. University of Nebraska Press, Lincoln.

Johnsgard, P. A. 1979. A guide to North American waterfowl. Indiana University Press, Bloomington, Indiana.

Lucas, Z. and I. A. McLaren. 1988. Apparent predation by Grey Seals, Halichoerus grypus, on seabirds around Sable Island, Nova Scotia. Canadian Field-Naturalist 102:675-678.

Madge, S. and H. Burn. 1988. Waterfowl; an identification guide to the ducks, geese and swans of the World. Houghton Mifflin, Boston.

Munro, J. A. 1929. Notes on the food habits of certain raptors in British Columbia and Alberta. Condor 3 1: 1 12-1 16.

Nowak, R. M. 199 1. Walker's mammals of the World. 5th edition. Volume 11. John Hopkins University Press, Baltimore.

Odlum, G. C. 1948. An instance of Killer Whales feeding on ducks. Canadian Field-Naturalkt 62:42.

Palmer, R. S. (Editor). 1976. Handbook of North American birds. Volume 3. Yale University Press, New Haven, Connecticut.

Phillips, J. C. 1922-1926. A natural history of the ducks. Houghton Mifflin, Boston (reprinted 1986 by Dover, New York).

Retfalvi, L. 1970. Food of nesting Bald Eagles on San Juan Island, Washington. Condor 72:358-36 1.

Rodgers, J. E. 1974. Birds of the Pacific Northwest. Volume 1. J. J. Douglas, Vancouver.

Schliemann, H. 1990. Earless seals. pages 212-242 in S. P. Parker (Editor). Grzimek's encyclopedia of mammals. Volume 4. McGraw-Hill, New York.

Todd, F. S. 1979. Waterfowl: ducks, geese & swans of the World. Harcourt Brace Janovich, New York and London.

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