McKinnon et al 2011 Reproductive success, moult and autumn migration of Wood Thrushes
1. The influence of reproductive success and moult on autumn migration strategy in a songbird Emily A. McKinnon1 Kevin C. Fraser1 Elizabeth A. Gow1,2 Maggie MacPherson1 Calandra Q. Stanley1 T. Kurt Kyser3 Bridget J. M. Stutchbury1 1York University, Toronto, Canada 2Current: University of Saskatchewan, Saskatoon, Canada 3Queen’s University, Kingston, Canada emilymck@yorku.ca 1
2. Outline Previous work on Wood Thrushes (Hylocichlamustelina) Double-brooding Migration using geolocators Research questions Methods: geolocators and SIA Results Conclusions and future work 2
4. Reproductive success and carry-over effects 86% of successful females attempt a second brood Costs for moult and migration? 4 E. Gow. Thesis, York University, Toronto, Canada E. Gow et al. submitted to Auk
5. Wood Thrush moult Energetic/time constraints at breeding sites could promote delayed moultor moult during migration 5
6. Wood thrush migration Rate Total (fall) stopover days Arrival dates Routes 6 Stutchbury et al. 2009 Science 323:896 Stutchbury et al. 2011. Proc. R. Soc. B. 278:131-137. Stutchbury Lab unpubl. data
8. Research Questions Does reproductive output influence moult and or fall migration? Is variation in fall migration strategy explained by moult south of breeding site? 8
9. Methods: reproductive output, moult Reproductive output measured by following nests in 2008 Moult scored in August (# of new feathers present/growing) Geolocators deployed on birds to collect data on migration 9
10. Methods: geolocator analysis Geolocator light data analysed for: fall migration rate (overall km/day) arrival date at winter site total number of fall stopover days 10
11. Methods: moulting south of breeding site 4 feathers in a moult sequence were sampled 11 Tertial clip Primary clip Secondary clip
12. Methods: stable-isotope analysis Feathers analysed for ratios of stable-hydrogen isotopes (δD) Birds classified as moult migrants if at least 1 feather grown south 12 δD
15. Does reproductive output does influence fall migration? Late breeders ( rep. output) farther N on 10 Oct Late fall migration departure No relationship between breeding and winter arrival Why? 14 Stutchbury et al. 2011. Proc. R. Soc. B. 278:131-137.
16. What predicts winter arrival? 15 Fall migration appears to be related to # stopover days. Why such long stopovers? Stutchbury et al. 2011. Proc. R. Soc. B. 278:131-137.
17. Evidence of moult south of breeding sites 16 5/31 (16%) individuals moulted feathers south of breeding sites δD www.waterisotopes.org
18. Moult and migration No significant differences in winter arrival date or migration rate Moult-migrants arrived later, migrated faster 17
19. Moult and migration No significant difference in # stopover days Moult-migrants had more stopover days 2 birds with > 3 week stopovers both grew feathers south 18
20. Conclusions High reproductive output delays moult, and perhaps fall migration departure High reproductive output does not influence winter arrival Winter arrival date driven by # stopover days 16% birds moulted feathers south; no significant relationship with migration rate, winter arrival or total stopover days However, small sample sizes and trends suggest more sampling needed 19
21. Implications and future work If not for moult, why do some WOTH take fall ‘vacations’? WOTH on extended stopover captured in Belize in October 2010 and radio-tagged physiology, body condition More geolocators and moult data: >100 geolocators deployed in Belize, Costa Rica, and Canada in 2011 + n=25 in-hand awaiting analysis Expect ~30-50 returns in winter 11/12 and summer 2012 20
23. Acknowledgements Funding: NSERC, York University, Molson Fund, Canada Research Chair, proceeds from Silence of the Songbirds Many hard-working field and lab assistants Queen’s Facility for Isotope Research (QFIR) 22
24. Does rep. success influence moult location? 5/8 double-brooded birds grew at least 1 feather S of breeding site 2/7 single-brooded birds show moult S of breeding site Not significantly different (X2 = 3.355, p = 0.07) Double-brooding does not appear to influence moult location. 23 E. Gow et al. submitted to Auk.
