The effects of early experience on the development, behavior, and survival of shorebirds

TitleThe effects of early experience on the development, behavior, and survival of shorebirds
Publication TypeThesis
Year of Publication1992
AuthorsPowell ANeva
DegreeDoctor of Philosophy
Number of Pages109 pp.
UniversityUniversity of Minnesota
CityMinneapolis, MN
KeywordsREPRODUCTIVE SUCCESS
Abstract

The objectives of my dissertation were twofold: (1) to determine how the early experience of captive reared and cross-fostered young plovers differed from that of young raised by their natural parents, and (2) to use this information to evaluate captive-rearing and cross-fostering as viable management tools for enhancing the reproductive success of small populations of shorebirds. The chapters that follow describe the work I did in anticipation of using population augmentation to supplement the endangered Great Lakes population of piping plovers (Charadrius melodus). Chapter I describes the habitat characteristics and reproductive success of piping plovers nesting on Great Lakes islands, where the majority of my field work was conducted. This chapter sets the stage for the justification of using population augmentation to enhance this endangered population as a model for techniques applicable to other Charadriid species. Islands were shown to be important to Great Lakes piping plovers because of the availability of wide, pristine, and undisturbed beach habitat. This chapter was published in The Wilson Bulletin. In Chapter II, I describe the captive rearing experiments I conducted using killdeer (Charadrius vociferus) as a surrogate species for piping plovers. Behavioral differences between captive-reared and wild killdeer were found, with captive chicks spending a greater proportion of time resting, and less time feeding, than wild chicks. This was attributed to the constant heat source and concentrated, high quality, food that was provided to captive-reared chicks. Growth rates and responses to alarm calls and potential predators were the same between groups. Hatching success and survival to fledging were significantly higher for captive-reared young. Because of precocial characteristics of young shorebirds, captive rearing was considered a viable tool for population enhancement. Political rather than biological obstacles are currently the issue in captive rearing. Chapter II is a short note on an observation I made of an eastern wood-pewee (Contopus virens) attempting to feed captive killdeer chicks. This observation was worthy of documentation because it is an extremely rare example of a species with altricial young "adopting" precocial chicks. This chapter was published in Journal of Field Ornithology in 1990. In Chapter IV, I compare the growth and behavioral development of parent-reared, cross-fostered, and captive-reared killdeer chicks. This chapter builds on the captive rearing aspect of Chapter II. Parent-reared chicks were raised naturally in the wild, cross-fostered chicks were raised by spotted sandpipers (Actitis macularia) in the wild, and captive-reared chicks were raised by humans. Hatching and fledging success were significantly increased by captive rearing, and cross fostering produced approximately the same number of fledged young as natural parent-rearing. Captive-reared killdeer chicks spent more time resting and less time feeding, and stayed closer to siblings than cross-fostered or parent-reared chicks: these behavioral differences were not seen after release to the wild. Growth rates among the three groups were similar. There was no evidence that captive-reared and cross-fostered killdeer were negatively affected by their early experiences. Captive rearing was recommended over cross fostering because captive rearing is more flexible as a technique, produces more young, does not affect another species, and does not produce potential imprinting problems. This chapter will be published in Conservation Biology. Finally, Chapter V compares the early experience of wild killdeer chicks with that of piping plover chicks. This chapter is the final justification of the applicability of surrogate experiments with killdeer to another species. Behavioral observations were made on eight families of each species. The brood-rearing behaviors of parent birds were similar for both species. Killdeer parents gave higher intensity antipredator displays, and moved broods over larger distances than piping plovers. C icks of both species had comparable behaviors and growth patterns.