ECOLOGY/EVOLUTION

Managing Murrelets

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Science  09 Feb 2007:
Vol. 315, Issue 5813, pp. 739
DOI: 10.1126/science.315.5813.739c

One challenge in conservation management is estimating what a sustainable population should look like. Geographic and genetic information can readily be obtained from museum specimens, but if, as for many birds, there are morphologically distinguishable age classes, then age-ratio analysis can also provide baseline rates for reproduction and survival. The output of such an analysis can be used to set targets for population recovery.

Beissinger and Peery have championed the case of the marbled murrelet (Brachyramphus marmoratus), an endangered seabird from the Californian coast which unexpectedly nests high up in old-growth coniferous trees and whose plight has only recently come to attention. The murrelet population is being decimated as a result of attacks from crows, by logging, and especially via the loss of the fish that they eat. Reproduction is expensive for murrelets; they lay a single egg that weighs up to a quarter of the adult bird's weight, and adults will abandon breeding in the face of insufficient food. There are some methodological risks with age-ratio analysis, but for this bird, contemporary data from field studies were compared with the museum data, which showed that the reproductive success of contemporary murrelets is almost an order of magnitude less than it was a century ago. — CA

Ecology 88, 296 (2007).

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