Shorebird life histories at multiple levels of analysis

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Organisms have diverse ways and schedules to survive and reproduce, referred to as their "life history strategies". This research addresses differences in life history strategies between species of small shorebirds, and also among individuals within species. When characters have strong effects on an organism's survival or reproductive success, population biologists are challenged to explain why genetic variation for such characters persists. This research explores mechanisms that permit coexistence of competing forms of such traits. I work primarily with differences in reproductive behaviour and migration behaviour of sandpipers, small shorebirds. Most of the research on reproductive behaviour involves a peculiar old-world sandpiper, the Ruff (Philomachus pugnax), in which three distinct types of males occur during the breeding season: (1) territorial males that fight for mating courts, (2) "satellite" males that do not fight, but are instead recruited to join with the normally territorial males on their courts, and (3) rare "female mimic" males, which neither flight nor display to females, but nonetheless do mate. We are studying how these three kinds of males maintain themselves in populations, how they obtain matings with females, how behaviour is regulated hormonally, and what genetic differences exist among types. Studies with related shorebird species ask why some females mate with several different males during a single breeding attempt. We are testing theories about how females may gain from having more genetically diverse offspring. In a final species, the Western Sandpiper, we are determining how migration distance affects future survivorship and reproductive rates. It appears that birds that migrate farther have higher survivorship, but breed less often, than those with shorter migrations, which would represent a "life history tradeoff". Understanding how different life histories persist helps us predict how adaptable species will be in the face of environmental changes.