Effects of El Nino Events on Darwin's Finch Productivity

Abstract

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Non–random fitness variation in two populations of Darwin's finches

“…The key question is: What governs longevity of the breeders ? Combining the present results with long-term ecological studies on the same island (Grant & Grant 1996;Grant et al 2000), we suggest the answer is that both life-history and morphological traits in£uence longevity in ways that vary depending upon £uctuations in environmental conditions. The particular factors and directions of selective in£uence change because the environment £uctuates from droughts and low food supply to an abundance of rain and enhanced food supply at approximately four-year intervals, or once per ¢nch generation on average (Grant & Grant 1992).…”

“…In the years 1979^1991 and 1998 an attempt was made to ¢nd every nest on the island throughout each breeding season and to band all the nestlings (Grant & Grant 1992;Grant et al 2000). From 1992 to 1997 we spent approximately the ¢rst half of each breeding season on the island.…”

“…Breeding, and the survival of o¡spring to breed (recruitment), vary greatly among years (table 1) as a result of annual £uctuations in rainfall and food supply in this seasonally arid environment (Grant & Grant 1996;Grant et al 2000). Entry into the breeding population occurred gradually over ¢ve years for members of the 1978 cohorts, abruptly after two years for 1981 cohorts and after as little as three months at rapidly rising density for 1983 cohorts (maximum four years).…”

Habitat selection and ecological speciation in Galápagos warbler finches ( Certhidea olivacea and Certhidea fusca )

“…This suggests that population size does not affect the detection of recent genetic movement, and a single wave of dispersal limited to C. fusca is unlikely. Reproductive surges that could lead to waves of dispersal are known in Darwin's finches, but have repeatedly been linked to recurring El Niñ o events (Grant et al 2000), which affect the entire archipelago, not subsets of islands. Although it is difficult to completely rule out more complex alternatives, habitat choice is the most parsimonious explanation for the observed patterns.…”

How climate change might influence the starvation–predation risk trade-off response

“…Higher temperatures reduce energy budgets (Calder & King 1974), affecting prey activity and accessibility, daily energy needs and the costs of foraging (e.g. Grant et al 2000;McGowan et al 2002;Sergio 2003;Yasue et al 2003), and so are likely to improve the quality of the winter foraging environment (Schaefer et al 2006;Wrona et al 2006;Wiegand et al 2008).…”