Comparative reproductive biology of sympatric species: Nest and chick survival of American avocets and black-necked stilts

Journal of Avian Biology
By: , and 

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Abstract

Identifying differences in reproductive success rates of closely related and sympatrically breeding species can be useful for understanding limitations to population growth. We simultaneously examined the reproductive ecology of American avocets Recurvirostra americana and black-necked stilts Himantopus mexicanus using 1274 monitored nests and 240 radio-marked chicks in San Francisco Bay, California. Although there were 1.8 times more avocet nests than stilt nests, stilts nonetheless fledged 3.3 times more chicks. Greater production by stilts than avocets was the result of greater chick survival from hatching to fledging (avocet: 6%; stilt: 40%), and not because of differences in clutch size (avocet: 3.84; stilt: 3.77), nest survival (avocet: 44%; stilt: 35%), or egg hatching success (avocet: 90%; stilt: 92%). We reviewed the literature and confirmed that nest survival and hatching success are generally similar when avocets and stilts breed sympatrically. In addition to species, chick survival was strongly influenced by age, site, and year. In particular, daily survival rates increased rapidly with chick age, with 70% of mortalities occurring ≤ 1 week after hatch. California gulls Larus californicus caused 55% of avocet, but only 15% of stilt, chick deaths. Differential use of micro-habitats likely reduced stilt chick’s vulnerability to gull predation, particularly during the first week after hatch, because stilts nested in vegetation 2.7 times more often than avocets and vegetation height was 65% taller at stilt nests compared with avocet nests. Our results demonstrate that two co-occurring and closely related species with similar life history strategies can differ markedly in reproductive success, and simultaneous studies of such species can identify differences that limit productivity.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Comparative reproductive biology of sympatric species: Nest and chick survival of American avocets and black-necked stilts
Series title Journal of Avian Biology
DOI 10.1111/jav.00385
Volume 45
Issue 6
Year Published 2014
Language English
Publisher Wiley
Contributing office(s) San Francisco Bay-Delta, Western Ecological Research Center
Description 15 p.
First page 609
Last page 623
Country United States
State California
Other Geospatial San Francisco Bay
Online Only (Y/N) N
Additional Online Files (Y/N) N