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Posted by Frank on 21:39:08 02/16/11
In Reply to: Pine Siskins and Biogeography posted by Alex Harper
Very well said! Just taking consideration the anole situation in the Miami area, the point about available (vacant) niches can be demonstrated. In places like Matheson Hammock, Vizcaya, and my own backyard in Little Havana, several anole species now coexist (and have so for many years) when formerly there was only one- the green anole. Each one has now partitioned the environment, just as they do in nearby West Indian islands. Of course, many argue that the green is disappearing due to the invasion of 'foreign' anoles, but in reality it is just occupying a much more narrow 'leaf' niche that its relatives on other islands occupy. Even with native (and North American temperate birds), this tropical environment effect is especially pronounced in Miami-Dade and Broward counties. The wintering warbler and other passerine (example-Sadowski)species is remarkable compared to only a hundred or so miles north (and west). And the equally remarkable rarity or absence of widespread Florida species- even wintering ones- in this little corner is equally striking. Case in point- I have seen many more black-throated blues in Miami during winter than ruby-crowned kinglets, goldfinches or robins! Although most exotics haven't gone too far, it seems to make sense that spot-brested orioles are filling the year-round flower niche that is mostly vacant in the summer. Native Baltimores and ruby-throats certainly benefit being here in the winter.
One last thing- in the 19 or so years that I've been here, I've noticed this tropical 'effect' has increased gradually. It does indeed seem that there have been less northern birds (even year round ones) around here than formerly- and more 'southern' -wintering and West Indian- ones around. Of course this could be because of the keen birding community watching for this stuff...
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