the incidence of lead shot ingestion by waterfowl in ireland

The Incidence of Lead Shot Ingestion by Waterfowl in IrelandAuthor(s): Douglas ButlerSource: The Irish Naturalists' Journal, Vol. 23, No. 8 (Oct., 1990), pp. 309-313Published by: Irish Naturalists' Journal Ltd.Stable URL: http://www.jstor.org/stable/25539531 .

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Ir. Nat. J. Vol. 23 No. 8 1990 mQ

Grunewald, J. (1972) Die hydrochemischen Lebensbedingungen der praimaginalen Stadien von Boophthora erythrocephala De Geer (Diptera: Simuliidae) I.

Freilanduntersuchungen. Z. Tropenmed Parasit 23 432-445.

' ' '

Ladle, M., Bass, J. A. B. & Jenkins, W. R. (1972) Studies on production and food consumption by the larval Simuliidae of a chalk stream. Hydrobiologia 39: 429-448.

Post, R. J. (1980) Cytotaxonomy of the Simulium ornatum species-group in Britain. Newsletter ofthe British Simulium Group 3: 3-5.

Schroder, P. (1988) Distribution patterns of blackfly (Diptera; Simuliidae) associations in two Irish river svstems Hydrobiologia 164: 149-160.

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-& Schweder, H. (1986) Kriebelmucken (Diptera: Simuliidae) im county Kerry, Siidwest Iriand Z angew. Ent. 96: 85-91.

THE INCIDENCE OF LEAD SHOT INGESTION BY WATERFOWL IN IRELAND

Douglas Butler

White Gables, Golden, Co Tipperary

In North America it has long been recognized that spent lead shot from hunters'

cartridges represents a potential threat to waterfowl. Lead pellets may be accidentally ingested as grit or selectively taken by mistake for certain seeds. According to Forbes and Sanderson (1978) a preponderance of evidence suggests that most ofthe lead pellets are eaten as food by waterfowl rather than as grit.

Ingested pellets are subjected to abrasion in birds' gizzards and in the presence of acidic digestive juices the lead is liable to enter solution. The resulting salts of the metal are absorbed both through the wall ofthe gizzard and the intestine. Death from lead poisoning

may occur. Where death does occur, it is as a result of a combination of paralysis, starvation and a range of specific metabolic damage to kidney, liver and a range of organs (Simpson et al. 1979). It must be recognized, however, that the presence of pellets in the gizzard does not necessarily mean that lead poisoning will occur as many factors combine to determine

the actual effect of ingested lead on a given bird.

Many large scale die-offs of waterfowl attributed to lead poisoning have been recorded in North America (Bellrose 1959, Hawkins 1965, Anderson 1975), In contrast, there have

been far fewer die-offs recorded in Europe. Thomas (1980) summarizes the known

European die-offs. There is no recorded incidence of a large scale die-off in Ireland

resulting from the ingestion of hunters' spent shot. However, O'Halloran et al (1988) record the death of 3 Whooper swans (Cygnus cygnus) at Kilcolman Wildfowl Refuge, Co

Cork, as a result of the ingestion of lead pellets from wiidfowling which took place there

more than 18 years earlier. These authors also found that 29 mute swans (Cygnus olor) died

following the ingestion of shotgun pellets at a clay pigeon shooting site in the vicinity of

Lough Neagh, Northern Ireland and that a further 20 mute swans suffered a similar fate in

this area in 1980. This present study involved the examination of the contents of 913 gizzards taken from

10 duck and 1 goose species. 847 of these gizzards were supplied by members of the

National Association of Regional Game Councils during the period 1 September 1986?31

January 1990. The remaining 66, which had been obtained during the period 1 September 1981 _31 January 1982, were suppliedby D. O'Keefe, Zoology Department, University

College Galway. Ducks may be divided into three groups according to their mode of feeding. These

three groups are composed of divers, dabblers and grazers. Studies in North America and

Britain (Bellrose 1959, Thomas 1975, Mudge 1983) have shownthatthe greatest number of

pellets are usually round in the gizzards of diving ducks. Somewhat fewer are found in

dabblers and the smallest numbers in grazing species.



310 Ir. Nat. J. Vol. 23 No. 8 1990

Table 1. County of origin of gizzards and number of sites sampled in each county.

County Number Number of County Number Number of

of gizzards sites of gizzards sites

Carlow 9 1 Limerick 14 2 Cavan 18 2 Longford 28 6

Clare 107 3 Meath 2 1 Cork 5 2 Offaly 17 3

Donegal 9 1 Tipperary 285 11 Dublin 30 4 Waterford 8 2

Galway 102 5 Westmeath 60 10

Kerry 13 1 Wexford 140 3 Kildare 1 1 Wicklow 31 3

Laois 33 3 Totals 913 65 Leitrim 1 1

Methods

Gizzards were removed by hunters and supplied frozen or preserved. Details of species and where the birds had been shot were included in each case. Table 1 shows the number of

gizzards obtained from each county and also the number of sites providing gizzards in each

county. A full list of sites is shown in the Appendix. Table 2 shows the number of gizzards obtained from each species. The disproportionate numbers of mallard, teal and wigeon gizzards reflect both the large wintering populations of these species and their popularity as hunters' quarry.

Gizzards were sectioned and the contents washed into a large, shallow enamel bowl.

Organic matter was then decanted off. Following this the remaining contents were sifted for lead pellets. As an aid to finding pellets the bowl was tilted slowly from side to side. The contents were then filtered and allowed to dry. They were then once again searched for

pellets. Because pellets may be 'shot in' as well as ingested, it was necessary to adopt two additional procedures: (1) each gizzard was inspected for puncture wounds; (2) the nature of the surface of each pellet found was noted. Bellrose (1959) notes that 'shot in' pellets have

angular edges and characteristic craters. In contrast, due to abrasion in the gizzard, ingested pellets have typically smooth surfaces.

O'Halloran et al. (1988) distinguished ingested angling lead from ingested shotgun lead on the basis that the former is of grey colour and flattened appearance whereas the latter is black and of round appearance. However, it is the experience of this author that, whilst 'shot in' and freshly ingested shotgun lead is usually black, pellets that have been ingested for some time and have undergone a considerable degree of abrasion are often grey in colour. In this study only two pellets were found which, on the basis of both colour and

shape, might qualify as angling lead rather than shotgun lead. These pellets were obtained from mallard gizzards, one from the North Slob, Co Wexford, and the other from New Inn, Co Tipperary. Both birds were shot in early September. However, despite their flattened

appearance, it is unlikely that either pellet was, in fact, of angling origin. In the New Inn area the traditional angling technique is that of fly fishing. As a result lead weights would not be a normal part of an angler's equipment. In the Wexford case a second ingested pellet taken from the gizzard displayed the more usual rounded form.

Results

Of the 913 gizzards examined, 23 were found to contain ingested pellets. The

percentages of gizzards containing ingested pellets were 0-78 for grazers, 2*05 for dabblers and 7*84 for divers. Overall, 2-52% of gizzards contained ingested pellets. In the case of the contaminated gizzards of diving ducks, 6 of the 8 found to contain ingested pellets came from one site. Table 2 shows the numbers of gizzards of each of the three feeding groups



Ir. Nat. J. Vol. 23 No. 8 1990 311

Table 2. Number of gizzards for each species containing ingested pellets and numbers of pellets

ingested by each species.

Species Number of Number Numbers of gizzards containing % pellets present

pellets Grazers

White-fronted goose (Anser albifrons) 3 0 ? ?

Wigeon {Anas penelope) 126 1 0.79 1

Total 129 1 0.78

Dabblers

Gadwall (Anas strepera) 4 0 ? ?

Mallard {Anas platyrhynchos) 371 11 2.96 5,4,4,2,2,1,1,1,1,1,1 Pintail (Anas acuta) 2 0 ? ?

Shoveler (Anas clypeata) 11 0 ? ?

Teal (Anas cret ca) 294 3 1.02 1,1,1

Total 682 14 2.05

Divers

Goldeneye (Bucephala clangula) 12 2 16.67 2 J Pochard (Aythya ferina) Al 3 6.38 7,6,1

Scaup (Aythya mart la) 1 1 14.28 1

Tufted duck (Aythya fuligula) 36 2 5.6 1,1

Total 102 8 7.84

Table 3. Sites from which contaminated gizzards were obtained and number of contaminated gizzards from each site.

County Site Number of Number of County Site Number of Number of

gizzards gizzards gizzards gizzards

containing containing

pellets pellets

Clare Doonbeg 81 3 Westmeath Lough Ree 12 1

Galway Bushypark 8 2 Lough Ennel 9 1

Lough Corrib 73 2 Wexford Wexford Harbour

Kerry Killarney 13 I and Slobs 118 8

Tipperary Golden 45 2 Wicklow Kilcoole 11 1

New Inn 83 2

which contained ingested pellets and the numbers of pellets found for each species. Fifteen of the 23 gizzards, representing 65*2%, contained a single pellet. The 23 contaminated

gizzards originated from 10 of the 65 sites investigated. Only two sites yielded more than 2

gizzards containing ingested pellets. Table 3 shows the sites from which contaminated

gizzards were obtained and the number of contaminated gizzards from each of these sites. 'Shot-in' pellets were found in 18 gizzards, representing 1*97% of the sample.

Discussion

The results of this survey suggest that the incidence of ingestion of spent shotgun pellets by waterfowl in the sites sampled in Ireland is low. Of the total sample only 23

gizzards, representing 2*52%, contained ingested pellets. Additionally, only 10 sites out of the 65 investigated yielded gizzards which contained pellets.

In relation to the feeding habits of the different waterfowl species, the trend observed elsewhere of decreasing incidence of pellet ingestion from divers, through dabblers to

grazers, was found to be paralleled in Ireland. Data for these three groups compare favourably with those obtained in Britain by Mudge (1983). The percentages of gizzards found by Mudge to contain ingested pellets were 0 for grazers, 2.46 for dabblers and 10.53 for divers. Irish equivalents were 0.78, 2.05 and 7.84.



312 Ir. Nat. J. Vol. 23 No. 8 1990

It may be argued that figures obtained by visual examination of gizzard contents

understate the true level of ingested lead as minute remains of abraded pellets may go unnoticed. Anderson and Brewer (1980) showed that such examination revealed only 76.8% of the mallard gizzards that were known, through the use of X-ray and fluoroscopy, to contain ingested pellets. The great majority of mallard and pochard gizzards investigated in this study contained large quantities of dark coloured grit. In consequence, it is possible that the data obtained for these species understates the true situation. However, in the case

of teal and wigeon the situation is rather different. Because teal gizzards contain very small amounts of grit it is unlikely that pellets are overlooked in the course of careful visual examination. In the case of wigeon, the gizzards are typically packed with silt or fine sand which provides a contrasting background against which to search for pellets. Therefore, for this species also, it is unlikely that pellets were missed during visual examination.

A number of studies have been carried out in order to assess the effects of ingested lead

pellets on waterfowl. The essential feature of these studies was the dosing of wild-caught ducks with varying numbers of pellets. Whereas Longcore et al. (1974) found that the

feeding of one No. 4 pellet resulted in mortality levels in the range 18%-20%, Sanderson and Irwin (1976) found that no mortality resulted when the same dose of lead was

administered with any one of three different diets. Bellrose (1959) showed that when mallard trapped on migration were fed one No. 6 pellet and then released, their subsequent dispersal was not significantly different from undosed controls.

It is therefore not unreasonable to assume that the ingestion of a single pellet is unlikely to cause mortality. However, it must be recognized that it may produce sub-lethal effects. A number of such sub-lethal effects have been reported by Mathiasson (1986) and O'Halloran et al. (1989). It may be noted that in this study 65.2% of contaminated gizzards contained

only one pellet. Because of the effect of lead poisoning on waterfowl populations, control measures

including a ban on the use of lead shot have been proposed/initiated elsewhere. This survey suggests that there is, as yet, no need for such control measures in Ireland.

Acknowledgements

I would like to thank all those who supplied gizzards for the survey. Special thanks to Dr J. Dunne for his criticism of an earlier draft of the manuscript.

REFERENCES

Anderson, W. L. (1975) Lead poisoning in waterfowl at Rice Lake, Illinois. J. Wildl. Managt. 39: 264-270

Anderson, W. L. & Brewer, P. A. (1980) Incidence of ingested shotgun shell pellets in Illinois mallards as

determined by radiology: 1979 season. Illinois Dept. of Conservation, Division of Wildlife Resource,

Investigations and Surveys Section Report. Bellrose, F. C. (1959) Lead poisoning as a mortality factor in waterfowl populations. Illinois Nat. Hist. Surv. Bull.

27: 235-288.

Forbes, R. M. & Sanderson, G. C. (1978) Lead toxicity in domestic animals and wildlife. In Nriagu, O. (ed) The

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Hawkins, A. S. (1965) The lead poisoning problem in the four flyways. In Wasted Waterfowl Missisippi Flyway Central Planning Committee Report.

Longcore, J. R., Andrews, R., Locke, L. N.,Bagley,G. E. & Young, L. T. (1974) Toxicity of lead and proposed substitute shot to mallards. U.S. Fish Wildl. Serv. Wildl. Res. Rep. 183.

Mathiasson, S. (1986) Lead in tissues and gizzards of Mute swans, Cygnus olor, from the Swedish West coast, with remarks on other heavy metals and possible additive and synergestic effects. Var Fageld Vdrld

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lr. Nat. J. Vol. 23 No. 8 1990 in

Sanderson, G. C. & Irwin, J. C. (1976) Effects of various combinations of lead: iron pellets dosed in wild-type captive mallards. Illinois Nat. Hist. Sun'. Bull.

Simpson, V, R., Hunt, A. E. and French, M. C. (1979) Chronic lead poisoning in a herd of Mute swans. Envir. Poll. 18: 187-202.

Thomas, G. J, (1975) Ingested lead pellets in waterfowl at the Ouse Washes, England, 1968-73. Wildfowl 26: 43-48.

Thomas, G. J. (1980) Review of ingested lead poisoning in waterfowl 1WRB Bull. 46:'43-60.

Appendix

Sites from which gizzards were obtained.

County Sites County Sites Carlow River Barrow Offaly Little Brosna Cavan 2 sites, locations not stated River Shannon Clare Doonbeg i site, location not stated

Quin Tipperary Ardfinnan Scariff Ballingarry

Cork Bandon Ballyclerihan Rosscarbery Ballylooby

Donegal Inch Boherlahan Dublin Portmarnock Cahir

Rogerstown Estuary Clogheen Skerries Golden Swords New Inn

Galway Bushypark Templeraore Clare river Thurles

Lough Corrib Waterford Cappoquin Oranmore Tallow

Rahasane Westmeath Lough Derravaragh Kerry Killarney Lough Ennel Kildare Athy Lough Gowna Laois Abbeyleix Lough Kinale

Portlaoise Lough Ree 1 site, location not stated Lough Sheelin

Leitrim Killargue Mullingar Limerick Askeaton Rathowen

Kilmallock RiverInney Longford Crosswater 1 site, location not stated

Lanesborough Wexford Gorey Lough Ree Wexford Harbour and Slobs

Mostrim 1 site, location not stated River Camlin Wicklow Arklow River Shannon Kilcoole

Meath 1 site, location not stated Newcastle

DISPLACEMENT OF THE NATIVE IRISH FRESHWATER AMPHIPOD GAMMARUS DUEBENI BY THE INTRODUCED

GAMMARUS PULEX

Jaimie T. A. Dick, Robert W. Elwood and Donna E. Irvine

Division of Environmental and EvolutionatyBiology, School of Biology and Biochemistry,

Queen's University^ Belfastt BT1r INN

Prior to 1958-9, three species of freshwater amphipod (Peracarida: Crustacea) were

present in Northern Ireland, namely, Gamnmrus dwebemU\^., G. lacustris Sars and

G. tigrinus Sexton (Strange and Glass 1979). During their 1976-7 survey, Strange and



the incidence of lead shot ingestion by waterfowl in ireland

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