Research in the Norris Lab


Understanding the factors that limit and regulate migratory populations requires knowledge of how events interact throughout the annual cycle. Some of our recent 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. Our theoretical work has emphasized the importance of both seasonal interactions and migratory connectivity to be able to accurately predict changes in population size of migratory animals. Using a variety of tracking techniques, we are currently examining year-round population dynamics in an island population of Savannah sparrows (Passerculus sandwichensis) located on Kent Island in the Bay of Fundy, NB and a population of Tree swallows (Tachycineta bicolor) in Long Point Provincial Park, ON. 

Selected publications

Betini, GS, Griswold, CG, Norris, DR. 2013. Carry-over effects,

sequential density dependence and the dynamics of populations

in a seasonal environment. Proc Roy Soc Lond B 280:


Taylor, CM & Norris, DR. 2010. Population dynamics in

migratory networks. Theoretical Ecology 3: 65-73.

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. J. Animal Ecology 78: 460-467.

Norris, DR & Taylor, CM. 2006. Predicting the

consequences of carry-over effects in migratory animals.

Biology Letters 2: 148-151.

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. Proc Roy Soc Lond B 271: 59-64.

Norris, DR, Marra, PP, Kyser, TK, Montgomerie, R &

Ratcliffe, LM. 2004. Reproductive effort, molting latitude

and feather color in a migratory songbird. Science 306:


Each year, billions of dollars are spent on conserving and managing migratory species worldwide. However, decisions on how to allocate funds for conservation are largely based on ad-hoc approaches or simple ranking methods. Our research seeks to integrate demographic and movement data across multiple stages of the annual cycle to develop optimal conservation strategies for migratory species. We use both theoretical- and empirical-based models to explore how various population parameters influence resource allocation decisions.

Selected publications

Sheehy, J, Taylor, CM & Norris, DR. 2011. The importance of stopover habitat for developing effective conservation strategies in migratory animals. J. Ornithology 152(S1): S161-S168.

Sheehy, J, Taylor, CM, McCann, KS & Norris, DR. 2010.

Optimal conservation of migratory animals: integrating

demographic information across seasons. Conservation

Letters 3: 192-202.

Martin, TM, Chades, I, Arcese, P, Marra, PP, Possingham,

HP & Norris DR. 2007. Optimal conservation of migratory

species. PLoS One 2(8): e751.

Optimal conservation planning in migratory animals

Understanding the factors that influence population abundance requires knowledge of how events are linked throughout the migratory cycle.  The primary obstacle, thus far, has been the inability to track individuals over large geographic distances.  Part of the research in our lab has been devoted to developing intrinsic markers such as stable isotopes and trace elements, identifying and understanding the mechanisms behind sources of variance in isotopes and trace elements, and developing statistical tools to assign individuals to specific locations.  The development of such markers has provided us with the ability to develop a species-specific isotopic basemap of North America that includes strontium isotopes, a trace element basemap for a migratory shorebird, and a range-wide connectivity map for a migratory songbird.

Example publications

Mitchell, GW, Newman, AEM, Wikelski, M & 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

Storm-Suke, A, Wassenaar, LI, Nol, E & Norris, DR. 2012. The

influence of metabolic rate on the contribution of stable

hydrogen and -oxygen isotopes in drinking water to Quail blood

plasma and feathers. Functional Ecology 26: 1111-1119.

Sellick, MJ, Kyser, TK, Wunder, MB, Chipley, D & Norris,

DR. 2009. Geographic variation in strontium and hydrogen

isotopes in avian tissues: implications for tracking migration.

PLoS One 4(3): e4735.

Betini, GS, Hobson, KA, Wassenaar, L & Norris, DR. 2009.

Stable-hydrogen isotope values in songbird nestlings:

effects of temperature, body size, and diet. Canadian

Journal of Zoology 87: 767-772.

Wunder, MB & Norris DR. 2008. Improved estimates of

certainty in stable isotope based geographic assignments

for tracking migratory animals. Ecological Applications 18:


Developing effective tools for tracking migratory animals

Identifying factors that limit the abundance of animals is a critical step towards diagnosing the causes of population decline.  However, for the overwhelming majority of species, we have little information about the historic dynamics of populations.  As a consequence, we face considerable uncertainty about how to discriminate among competing hypotheses of population trend and how to design reliable conservation plans.  Over the last few years, we have developed a comprehensive diet history of Marbled murrelets (Brachyramphus marmoratus) spanning over 150 years. This allows us to examine the causes of variation in population abundance and determine how diet quality is influence by variation in climate.  We are also examining the diet history of a variety of other seabird species that breed in Canada.

Selection publications

Gutowsky, SE, Janssen, MH, Arcese, P, Kyser, TK,

Ethier, D, Wunder, MB, Bertram, DF, McFarlane

Tranquilla, L, Loughheed, C & Norris, DR. 2009. Concurrent

declines in nestling diet quality and reproductive success in

a threatened seabird over 150 years. Endangered Species

Research 9: 247-254.

Norris, DR, Arcese, P, Preikshot, D, Bertram, DF & Kyser,

TK. 2007. Diet reconstruction and historic population

dynamics in a threatened seabird. Journal of Applied

Ecology 44: 875-884.

Reconstructing population dynamics of seabirds

Seasonal interactions and population dynamics of migratory animals

The evolution of migration

Migration is one of the most fascinating behaviours found in nature, but how it evolved in such a wide variety of taxonomic groups and geographic locations has largely remained a mystery.  In collaboration with Caz Taylor and Cort Griswold, one approach our lab has taken for understanding why migration is so common is to develop theoretical models that produce quantitative predictions for the demographic conditions under which migration is expected to evolve from a resident (sedentary) ancestral population.  A second approach we use is to examine the costs and benefits of migratory behaviour in the wild. In collaboration with Alice Boyle and Chris Guglielmo, we test hypotheses related to the proximate and ultimate evolution of migration in a partially migratory population of White-ruffed manakins in Costa Rica.

Selected publications

Griswold, CG, Taylor, CM, & Norris, DR. 2011. The equilibrium population size of a partially migratory species and its response to environmental change. Oikos 120: 1847-1859.

Boyle, WA, Norris, DR & Guglielmo, CG. 2010. Storms

drive altitudinal migration in a tropical bird. Proc Roy Soc

Lond B 277:2511-2519.

Griswold, CG, Taylor, CM & Norris, DR. 2010. The evolution

of migration in a seasonal environment. Proc Roy Soc Lond B

277: 2711-2720.

Taylor, CM & Norris, DR. 2007. Predicting conditions for

migration: effects of density-dependence and habitat

quality. Biology Letters 3: 280-283.