Understanding the factors that limit and regulate migratory populations requires knowledge of how events interact throughout the annual cycle. Some of our empirical work using stable isotopes has provided evidence that the quality of habitat and diet during the non-breeding period in passerines and seabirds can influence reproductive success in the subsequent breeding season. We have also been examining seasonal interactions in resident species, such as the winter-breeding Gray Jay. Our theoretical work has emphasized the importance of seasonal interactions to be able to accurately predict changes in population size of migratory animals. Our recent experimental work in the laboratory has shown how density in one season can carry over to have non-lethal effects on individuals the following season and how this can influence long-term population dynamics. Using a variety of techniques, we continue to work both in the laboratory and the field to understand how non-lethal effects across seasons can influence fitness and population abundance.

Selected Publications

Sutton, AO, Strickland, D, Freeman, NK, Newman, AEM & Norris, DR. 2019. Fall freeze-thaw events carry over to depress late-winter reproductive performance in Canada Jays. In press: Royal Society, Open Science

Gow, EA, Burke, L, Winkler, DW, Knight, SM, Bradley, DW, Clark, RG, Belise, M, Berzins, L, Blake, T, Bridge, ES, Dawson, RD, Dunn, PO, Garant, D, Holroyd, G, Hussell, DJT, Lansdorp, O, Laughlin, AJ, Leonard, ML, Pelletier, F, Shutler, D, Siefferman, L, Taylor, CM, Trefry, H, Vleck, CM, Vleck, D, Whittingham, LA & Norris, DR. 2019. A range-wide domino effect and resetting of the annual cycle in a migratory songbird. Proceedings of the Royal Society, London: Biological Sciences 286:20181916.

Elliott, KH, Betini, GS & Norris, DR. 2017. Fear creates an Allee effect: experimental evidence from seasonal populations. Proceedings of the Royal Society, London: Biological Sciences 284:20170878.

Gomez, C, Bayly, N, Norris, DR, McKenzie, SA, Taylor, PD, Hobson, KA, Rosenberg, KV & Cadena, CD. 2017. Fuel loads acquired at a single stopover site carry over to influence the pace of intercontinental migration in a boreal songbird. Scientific Reports 7:3405.

Woodworth, BK, Newman, AEM, Turbek, SP, Dossman, BC, Hobson, KA, Wassenaar, LI, Mitchell, GW, Wheelwright, NT & Norris, DR. 2016. Differential migration and the link between winter latitude, timing of migration and breeding in a songbird. Oecologia 181: 413-422.

Elliott, KH, Betini, GS, Dworkin, I & Norris, DR. 2016. Experimental evidence for within- and cross-seasonal effects of fear on survival and reproduction. Journal of Animal Ecology 85: 507-515.

Pakkala, JJ, Norris, DR, Sedinger, JS & Newman, AEM. 2015. Experimental effects of early-life corticosterone on the HPA axis and pre-migratory behaviour in a wild songbird. Functional Ecology 30: 1149-1160.

Betini, GS, Pardy, A, Griswold, CK & Norris, DR. 2015. Causes and consequences of density-dependent dispersal: the role of seasonality and carry-over effects. Ecosphere 6(12): art 272.

Betini, GS, Griswold, CG, Prodan, L & Norris, DR. 2014. Body size, carry-over effects, and survival in a seasonal environment: population consequences. Journal of Animal Ecology 83: 1313-1321.

O’Conner, CM, Norris, DR, Crossin, GT & Cooke, SJ. 2014. Biological carry-over effects: linking comment concepts and mechanisms in ecology and evolution. Ecosphere 5(3): art28.

Betini, GS, Griswold, CG & Norris, DR. 2013. Density-mediated carry-over effects explain variation in breeding output across time in a seasonal population. Biology Letters 9(5): 20130582.

Betini, GS, Griswold, CG & Norris, DR. 2013. Carry-over effects, sequential density dependence and the dynamics of populations in a seasonal environment. Proceedings of the Royal Society, London: Biological Sciences 280: 20130110.

Mitchell, GW, Wikelski, M, Newman, AEM, & Norris, DR. 2012. Timing of breeding carries over to influence migratory departure in a songbird: an automated radiotracking study. Journal of Animal Ecology 81: 1024-1033.

Harrison, XA, Blount, JD, Inger, R, Norris, DR, Bearhop, S. 2011. Carry-over effects as drivers of fitness differences in animals. Journal of Animal Ecology 80: 4-18.

Sorenson, MC, Hipfner, JM, Kyser, TK & Norris, DR. 2009. Carry-over effects in a Pacific seabird: stable isotope evidence that non-breeding diet quality influences reproductive success. Journal of Animal Ecology 78: 460-467.

Norris, DR & Marra, PP. 2007. Seasonal interactions, habitat quality and population dynamics in migratory birds. Condor 109: 535-547.

Norris, DR & Taylor, CM. 2006. Predicting the consequences of carry-over effects in migratory animals. Biology Letters 2: 148-151.

Norris, DR. 2005. Carry-over effects and habitat quality in migratory animals. Oikos 109: 178-186.

Norris, DR, Marra, PP, Kyser, TK, Montgomerie, R & Ratcliffe, LM. 2004. Reproductive effort, molting latitude and feather color in a migratory songbird. Science 306: 1249-1250.

Norris, DR, Marra, PP, Kyser, TK, Sherry, TW & Ratcliffe, LM. 2004. Tropical winter habitat limits reproductive success on the temperate breeding grounds in a migratory bird. Proceedings of the Royal Society, London: Biological Sciences 271: 59-64.