Oversummering Juvenile and Adult Semipalmated Sandpipers in Perú Gain Enough Survival to Compensate for Foregone Breeding Opportunity

Resource type
Date created
2020-10-27
Authors/Contributors
Abstract
Background Age at maturity and the timing of first breeding are important life history traits. Most small shorebird species mature and breed as ‘yearlings’, but have lower reproductive success than adults. In some species, yearlings may defer northward migration and remain in non-breeding regions (‘oversummering’) until they reach 2 years of age. Some adults also oversummer. Oversummering would be favoured by natural selection if survival were as a result raised sufficiently to compensate for the missed breeding opportunity. Several thousand Semipalmated Sandpipers (Calidris pusilla) spend the non-breeding period at Paracas, Perú, including individuals with long bills (likely from eastern Arctic breeding populations ~ 8000 km distant) and short bills (likely from western Arctic breeding populations, up to 11,000 km distant), with short-billed birds more likely to oversummer. We tested the prediction that oversummering birds have higher survival than migrants, and that the magnitude of this higher survival for oversummering birds is enough to compensate for their lost breeding season.Methods We used a Multi-State Mark-Recapture model based on 5 years of encounter data (n = 1963 marked birds, and 3229 resightings) obtained year-round at Paracas, Perú, to estimate seasonal (i.e. breeding and non-breeding) survivorship for migrant and oversummering birds. We calculated the magnitude of the oversummering survival advantage required to compensate, for both yearlings and adults, based on published measures of annual survival and reproductive success. Using bill length as a proxy for migration distance, we investigated whether migratory survival is distance-dependent.Results We estimate that 28% of yearlings and 19% of adults oversummer. Survival is higher for oversummering birds than for migrants, and the oversummering survival advantage is greater for adults (0.215) than for yearlings (0.140). The theoretical thresholds predicted by the size of the missed reproductive opportunity are 0.240 for adults and 0.134 for yearlings. Migratory survival decreases and the oversummering rate increases with migration distance, as assessed by culmen length.Conclusions Our results support the life history hypothesis that oversummering raises survival enough to compensate for the loss of a breeding opportunity. Greater migration distance lowers survival and increases the probability of oversummering.
Document
Identifier
DOI: 10.1186/s40462-020-00226-6
Published as
Tavera, E. A., Stauffer, G. E., Lank, D. B., & Ydenberg, R. C. (2020). Oversummering juvenile and adult Semipalmated sandpipers in Perú gain enough survival to compensate for foregone breeding opportunity. Movement Ecology, 8(1), 42. https://doi.org/10.1186/s40462-020-00226-6.
Publication title
Movement Ecology
Document title
Oversummering Juvenile and Adult Semipalmated Sandpipers in Perú Gain Enough Survival to Compensate for Foregone Breeding Opportunity
Date
2020
Volume
8
Issue
1
Publisher DOI
10.1186/s40462-020-00226-6
Copyright statement
Copyright is held by the author(s).
Scholarly level
Peer reviewed?
Yes
Language
Member of collection
Attachment Size
s40462-020-00226-6.pdf 2.37 MB