conservation_shortened

conservation_shortened - Conservation: The plight (?) of...

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Conservation: The plight (?) of migrant birds Why Neotropical migrants should be ” in trouble They live in (and require) “two worlds” They are concentrated on wintering grounds Tropical deforestation is proceeding rapidly They spend more time on wintering grounds than on breeding grounds Hooded Warbler John Terborgh (1990)
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Why population declines in migratory birds are hard to detect Signal-to-noise problem . (If bird populations are not in equilibrium, gradual trends will be hard to see.) Local changes in populations versus changes on much larger scales. How do we detect the latter? “Floaters ” – they can mask population changes. The story of the “Maine gunners” Unmated males . How common are they and how to count them? A question of ethics: How picky should we be about evidence?
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What are the threats? 1. Habitat Destruction (of course) 2. Brown-headed cowbirds Populations are increasing and range is expanding Rates of parasitism can be very high (90% of Bell’s vireo nests in a TX site) BUT Host populations are often not impacted. It’s unclear why not. Re- nesting? High nest predation? Predictions about which species
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conservation_shortened - Conservation: The plight (?) of...

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