Friday, December 16, 2011

2011: International Year of Forests...Forest birds and neo-tropical connections

In Missouri, 428 species of birds have been recorded. 

One hundred and seventy of those species breed here every year; 84 of them leave Missouri for the winter and 58 of them go further and leave the United States.  The latter include what is called neo-tropical migrants.  Unfortunately many neo-tropical birds have suffered population declines since the ‘60s (when tracking birds first started).  Many songbird populations are half of their 1965 populations.
A Ruby-throated Hummingbird--possibly one of the best known of the neo-tropical migrants
Missouri forests, and wildlife resources in general, have made a remarkable recovery from the early 20th century.  In the past 20 years, Missouri has had an increase of 1 million acres of forested land--making a total of 14 million acres.  Still, forest fragmentation may play a role in the survival of certain bird populations.   Fragmentation is a discontinuity of a particular type of habitat and forest fragmentation increases with land-use conversion.

For example, forest fragmentation in many areas has put brown-headed cowbirds in closer proximity to forests, when historically they were found in open land and grassland habitats, like the great plains.  Brown-headed cowbirds use brood parasitism as a nesting strategy.  Females will lay eggs in the nests of other bird species.  These host birds will usually end up raising the cowbird at the expense of their own young.  Many open land and grassland species have learned to recognize the cowbird’s egg and push it out, but forest birds are not familiar with them.  Cowbird eggs hatch earlier, grow faster and often push the host young and/or eggs out of the nest.  This is just one example that can over time reduce the populations of forest birds. 
Brown-headed Cowbirds parasitize the nests of native birds
Habitat loss is also occurring in wintering grounds in Mexico, Central and South America, where our neo-tropical migrants may spend up to 8 months.  Much of Central America has been converting from independent farming to large-scale agriculture and non-sustainable timber harvesting.  Also, not helping the situation is the continuous human population increases, putting more pressure on the already stressed land.

The Missouri Department of Conservation has built partnerships with states and countries with shared bird species.  Four main bird conservation initiatives are the leaders in coordinating efforts on managing habitats and learning more about species: Partners in Flight, North American Waterfowl Management Plan, US Shorebird Conservation Plan and North American Water Bird Plan.  These sources help guide state and federal agencies, non-governmental organizations and industries on land management issues, and help rank the species and habitats by priority for conservation concern. 

Submitted by Sara Oliver, World Bird Sanctuary Naturalist

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