Migratory Birds: Ecology and Conservation. A report on the

BOU’s Annual Conference held at the University of Leicester

5-7 April 2011.

Jenny C. Dunn

RSPB, The Lodge, Potton Road, Sandy, Bedfordshire. SG19 2DL.

In April 2011, the British Ornithologist’s Union’s annual conference

took place at the University of Leicester. The theme of this year’s

conference was the ecology and conservation of migratory birds,

and talks ranged from those focussed on either breeding, migration

or wintering ecology, to those linking two or more of these and

trying to build a more complete picture of the complex problems

faced by long distance migrants. Talks also covered recent

technological advances, which are increasingly allowing us

intriguing new insights, particularly into the seasonal movements

and wintering areas of some of the most declining species. Finally,

talks examined the policy challenges associated with protecting

migratory species and how best to tackle flyway-scale conservation

of migratory birds.

The talks highlighted the progress made in expanding our

knowledge of migratory routes and related staging and wintering

areas, thanks initially to the contribution of recovery information

from ringing studies, and more recently to advances in technology

such as geolocators and satellite tags (Baillie et al. 2009). These

techniques offer the ability to track individual birds throughout the

entire annual cycle, linking ecology on both breeding and wintering

grounds (Robinson et al. 2010) and providing crucial information

for the design of effective conservation strategies (Martin et al.

2007). However, as always, the amount that is still unknown was

also emphasised: much of this knowledge will be critical in aiding

our understanding of species’ ecology and thus increasing our

ability to effectively conserve migratory birds (e.g. Faaborg et al.

2010a).

The conference began with a welcome address by the BOU

President Dr Alistair Dawson and was followed by a keynote speech

by Professor Ian Newton OBE FRS FRSE entitled “The ecology of

bird migration patterns”. Professor Newton’s talk gave an

introduction to the history of research and knowledge of migratory

birds, as well as serving to highlight the differences between

obligate and facultative migrants. Obligate, or fixed, migrants

follow a fixed migration route, with individuals often returning to

the same breeding and wintering grounds year after year, a trait

thought to be largely under genetic control (Newton 2008). In

contrast, facultative, or irruptive migrants tend to migrate when a

declining food supply demands it, and show huge variation in both

timing of migration and migration route, differing even in the

direction of migration from year to year (Newton 2006).

Facultative migrants also show very little breeding or winter site

fidelity, as revealed by ring recoveries and stable isotope analyses

(Marquiss et al. 2008). Finally, Professor Newton suggested that

obligate and facultative migrants should be regarded more as a

continuum, rather than two distinct entities, citing the case of the

White Stork Ciconia ciconia which appears to have both an obligate

and a facultative section to its migration strategy (Berthold et al.

2004), continuing to wintering grounds further south if necessary

in order to take advantage of food availability.

The first three sessions of the conference focussed on migration

ecology, and the first of these opened with a keynote presentation

from Dr Peter Marra (Smithsonian Migratory Bird Center,

Washington) examining the implications of carry-over effects

between seasons, and between breeding and wintering grounds

(e.g. Inger et al. 2010). This talk emphasised the importance of

taking into account the entire annual cycle of migratory birds when

considering any aspect of their ecology, as seasonal interactions

may be common (Norris & Marra 2007, Reudink et al. 2009) and in

general, research has tended to focus on the breeding season

rather than at other stages of the annual cycle (Faaborg et al.

2010b). Satellite tracking technology has greatly increased our

ability to track the movements of individuals in some detail for long

periods, and the next talk by Dr Kaspar Thorup (Natural History

Museum of Denmark, University of Copenhagen, Denmark)

summarised data from a satellite tracking study, examining the

influence of perpendicular wind on the migration of first year

raptors as distinct from adults (Thorup et al. 2003). The raptor

theme was continued by Matias Juhant (University of Maribor,

Slovenia), who discussed the scarcity of knowledge regarding

raptor migration within South America, and emphasised the

importance of establishing monitoring programmes using migration

counts (Juhant 2010).

Dr Ulf Ottosson (A. P. Leventis Ornithological Research Institute &

University of Lund, Sweden) opened the second session, describing

a study of Garden Warblers Sylvia borin, trying to piece together

the story of this species’ migration through a series of ringing-

recapture sites in Africa and providing substantial insight into the

over-winter ecology of this species (Ottosson et al. 2005b). The

timing of migration has long been known to be under the control of

both exogenous and endogenous factors (Styrsky et al. 2004), but

how these interact to influence migration timing is less well known.

This was the focus of the next talk from Miren Andueza (University

of Valencia & Aranzadi Science Society, Spain) who described a

study of exogenous and endogenous factors in Sedge Warbler

Acrocephalus schoenobaenus migration, emphasising the

importance of considering all factors together, rather than each

separately, as additive effects may be common. The next talk from

Dr Volker Salewski (University of Osnabrück, Germany) discussed

the difficulties of differentiating between Eastern Iduna pallida and

Western Olivaceous warblers I. opaca (Ottosson et al. 2005a), and

of distinguishing resident from migrant populations of both species,

highlighting some of the complexities associated with

understanding the migration ecology of these two species. The use

of stable isotopes has increased dramatically over the past decade,

especially in North America (Bowen et al. 2005); however, their use

in Afro-Palaearctic migrants is less well developed. Dr Paul Donald

(RSPB, UK) spoke about stable isotope work trying to identify the

winter distribution of the Aquatic Warbler Acrocephalus paludicola

by comparison of stable isotope feather signatures with those of

resident African species within the same trophic guild (Flade et al.

in press). This talk also highlighted some of the difficulties with

this technology, such as the requirement for a detailed knowledge

of moulting ecology, pointing out that moulting areas and wintering

grounds are not necessarily the same. Consequently, these data

need to be accompanied by other complementary approaches,

followed by fieldwork to confirm likely wintering locations

(Buchanan et al. in press). Dr Elizabeth Yohannes (Max Planck

Institute for Ornithology, Germany) continued the stable isotope

theme with her talk providing an overview of the use of stable

isotopes in avian migration work, and citing an example of hybrid

Great Acrocephalus arundinaceus and Clamorous A. stentoreus

Reed Warblers with features of both species, where stable isotope

analysis enabled the location of hybrid wintering grounds to be

established (Yohannes et al. 2011).

The final migration ecology session began with a talk from Dr Rob

Robinson (BTO, UK) looking at large scale patterns of demographic

responses to climate change in Palaearctic warblers. For example,

decreased productivity in woodland species, where temperature

change was most rapid, suggested mismatches with the seasonal

peak in food availability. Similarly, increased productivity of reed-

dwelling species, where temperature change was greatest,

suggested that this habitat may be thermally limiting and

consequently that survival is responsible for population changes in

these species. The second talk in this session was from Dr

Fernando Spina (Istituto Nazionale per la Fauna Selvatica, Italy),

looking at fat reserves in Barn Swallows in relation to the timing of

roosting and migration. Dr Spina illustrated a relationship between

fat reserves and the size of habitat barriers, for example, deserts or

seas, along migratory routes, revealing that both adult and juvenile

birds with larger barriers to cross had larger fat reserves (Rubolini

et al. 2002). Teresa Militão (University of Barcelona, Spain)

followed this by discussing whether stable isotope analysis can be

used to trace migratory routes of Atlantic seabirds and concluded

that this method can detect species-specific migratory strategies,

but that knowledge of individual species’ moult strategies was

crucial in interpreting these data (Ramos et al. 2009). Dr Rob

Sheldon (RSPB, UK) closed this session by describing work using

satellite tags to establish the migration routes of the Sociable

Lapwing Vanellus gregarious, a species for which hunting on

migration has been identified as the key threat to the population.

Data from satellite tracking has enabled survey and monitoring

work to be targeted at key sites along the migratory routes used by

this species and hence provide crucial information that will aid the

development of appropriate conservation actions.

Dr Jenny Gill (University of East Anglia, UK) opened the next

session of talks, aimed at discussing responses to environmental

change, with a keynote presentation looking at the population-level

responses of migratory birds to environmental change, focussing

on the Black-tailed Godwit Limosa limosa. This long-term study

investigates the drivers of “seasonal matching” in this species,

where breeding and non-breeding ground habitat show marked

variation in terms of breeding success and over-winter survival,

and a very strong relationship exists between winter and summer

habitat quality within individuals (Gunnarsson et al. 2005). Strong

seasonal matching is seen only in males, not females and

consequently it is thought to be driven by natal site fidelity and

may have profound implications in terms of inflating fitness

inequalities driven by habitat quality (Gunnarsson et al. 2005).

Next, Professor Brian Huntley (University of Durham, UK)

described work utilising 20 years of survey data to create models

predicting distributional responses to climate change in migrant

species. These models predicted shifts in both breeding and non-

breeding ranges resulting in a predicted 25% increase in migratory

distance (Doswald et al. 2009), although a change in migratory

strategy was proposed as an alternative possibility, whereby sub-

Saharan migrants could potentially winter north of the Sahara as

habitat becomes suitable. Alternatively, birds may respond to an

increased availability of habitat suitable for breeding and wintering

and consequently become resident in part of their range. Adam

Seward (University of Cardiff, UK) followed this by presenting

results from supplementary feeding experiments in breeding

Northern Wheatears Oenanthe oenanthe, where pairs provided

with supplementary food were more likely to have an extra

breeding attempt, and recruit offspring into the breeding

population.

The second day opened with a second session discussing responses

to environmental change and began with a talk by Dr Silke Bauer

(Swiss Ornithological Institute, Switzerland) looking at how

environmental change might affect the departure cues used by

birds in timing their migration. This talk emphasised how little we

know about the external cues affecting departure dates of migrants

and the need to develop a greater understanding of these cues

before we can predict the consequences of environmental change

for migrant species. Catriona Morrison (University of East Anglia,

UK) continued this session by discussing contrasting population

trends between Willow Warblers Phylloscopus trochilus in Scotland

and the south east of England (Morrison et al. 2010), with nest-

specific rainfall data showing high failure rates in warm and dry

conditions. Urbanisation causes changes in microclimate that may

impact upon bird behaviour through higher temperatures and

greater food availability (Partecke & Gwinner 2007), and Mikkel

Kristensen (Copenhagen Natural History Museum, Denmark)

discussed the possibility of distinct migration behaviour between

urban and rural birds. Urban populations did appear to have

adapted to these changes, with both blackbirds and great tits

reducing their migration distance compared to their rural

counterparts, and urban blackbirds showing a decrease in the

number of migrating individuals, suggesting a higher degree of

residency. Next, Dr Juliet Vickery (RSPB, UK) discussed early

results of a large-scale project in Ghana and Burkina Faso

monitoring migrants across a range of habitat types and

highlighted the importance of using multiple conservation tools,

considering socio-economic impact of conservation actions, and

taking a co-ordinated flyway approach when dealing with migratory

species. This session was concluded by a Techspot from Vicky

Jones (Birdlife International) introducing the Critical Site Network

Tool, a tool for conservation planning and management of

waterbirds accessible at www.wingsoverwetlands.org/csntool.

The next session focussed on the practicalities of putting science

into practice in terms of management for migratory birds, and

began with a talk from Dr José Alves (University of East Anglia, UK)

looking at the energetic costs of geographic variation in Black-

Tailed Godwit wintering grounds, and showing that the costs of

migrating longer distances and over-wintering further south are

outweighed by lower energetic living costs and reflected in an

earlier arrival date on breeding grounds and an increased

reproductive success. Dr Nigel Clark (Delaware Shorebird Project

& BTO, UK) followed this by describing the difficulties involved in

establishing compromise between interested parties where

overfishing of Horseshoe Crabs Limulus polyphemus at the final

stopover site for Red Knot Calidris canutus in Delaware Bay has led

to a catastrophic decline of this species (Haramis et al. 2007).

Whilst no long-term management solution has yet been established,

a major hurdle has been overcome as fishery groups now

appreciate that management of Horseshoe Crab fishing is essential

for the recovery of Red Knot populations. Conference talks then

moved on to the implementation of conservation through policy,

focussing first on the construction of Species Action Plans (SAPs),

with Tim Jones (DJEnvironmental, UK) discussing the problems

faced when constructing and implementing action plans for

migratory species, emphasising the need for international

supported and cooperation and a mutual shared will over a large

geographic scale. Dr Norbert Schäffer (RSPB, UK) described one

example of a successfully implemented action plan, the EU SAP for

the Corncrake Crex crex, which was largely driven by changing

mowing practices in the breeding areas to enhance nestling

survival (Schäffer & Weisser 1996). Many lessons learned from the

Corncrake SAP have been incorporated during the development of

the SAP for the Aquatic Warbler: SAPs are more likely to be

successful when a species faces similar problems across its whole

range, and when the SAP is ‘owned’ by an individual or institution,

and driven by the chairman of the working group. Dr Tim Stowe

(RSPB, UK) concluded this session by examining practical

approaches to implementing conservation strategies for African-

Eurasian migrants, emphasising that whilst an international

agreement is a very important start it needs to be complemented

by action on the ground at regional and national levels. The

identification of key wintering and stopover sites are particularly

important for waders and soaring birds; however, there are still

many unanswered questions regarding the migration of passerines

which migrate on a broad front, and conservation resources need

to be focussed on identifying key habitats and locations in the sub-

Saharan region in order to gain a greater understanding of factors

influencing population declines of these species.

Professor Franz Bairlein (Institute of Avian Research, Germany)

opened the final session, discussing future knowledge and policy

needs, with a key-note presentation discussing current knowledge

and future perspectives for the effective conservation of migratory

birds. Professor Bairlein’s talk emphasised the importance of

stopover sites and concluded by stressing the importance of

integrating theory with reality and identifying the mechanisms

driving population trends for each species. Declining population

trends are generally associated with a lack of adaptation to

changing conditions; however, Professor Hanna Kokko (Australian

National University, Australia) pointed out that interpretation of

population trends resulting from environmental change can be

tricky, citing a model of partial migration in Finnish Skylarks

Alauda arvensis where a higher proportion of the population

remaining resident as a result of climate change could potentially

lead to population declines as a result of increased adaptation. The

final talk of the conference was from Dr Ian Bainbridge (Scottish

Natural Heritage, UK), examining future projections for the

requirements of migratory birds. Future conservation strategies

need to take into account both daily and annual cycles; however,

policy tends to be less effective across annual cycles and site-based

conservation measures work better for some species than others,

highlighting the need for flexibility. Site-based conservation is

particularly difficult when species are mobile over-winter and

frequently a lack of knowledge as to the location of wintering

grounds hampers conservation efforts. Human population growth,

with it’s associated habitat destruction and degradation is likely to

be one of the biggest problems restricting conservation effort for

migratory birds.

Dr Danaë Sheehan rounded off the conference with a summary,

reviewing the approaches, challenges, and priorities for future

research highlighted throughout the conference. Many challenges

were suggested: one of the main priorities should be seen as

getting these issues onto the agendas of multilateral agreements

and making them effective. Research priorities tended to focus on

factors on wintering grounds – such as identifying key drivers of

population trends, investigating socioeconomic drivers, habitat

choice, and factors driving variation in seasonal survival and

regional variation in population trends. Investigating factors

driving declines in migratory seabirds, managing water and

wetlands for migrants in a changing climate, and establishing the

effects of climate change on productivity and migration strategies

were also among those issues highlighted as research and

conservation priorities.

The BOU awarded prizes for the best student poster and talk at the

conference. The prize for best student poster went to Helen

Anderson for her poster entitled “The benefit of early arctic

snowmelt for Pink-Footed Geese”, and best student talk to Teresa

Militão for her talk on stable isotope analysis and the migration of

Atlantic seabirds.

A conference like this could not take place without an efficient

organising committee, and thanks go to Dr Helen Baker (JNCC), Dr

Danaë Sheehan (RSPB), Dr Jacquie Clark (BTO), Dr Karl Evans

(University of Sheffield), Dr Peter Jones (Edinburgh University), Dr

Phil Atkinson (BTO), Steve Dudley (BOU) and Angela Langford

(BOU) for the smooth running of an extremely successful

conference.

Acknowledgements

References

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