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Posted by Alex Harper on 19:58:47 02/16/11
In Reply to: Pine Siskins in Collier County posted by Toe
Continentality, even in peninsular Florida, plays a role in inland climate versus coastal climate. The more xeric geology (and resultant fauna) and temperate climate of inland southwest Florida is likely more favorable for the Pine Siskins.
On the other hand, if it weren't for coastal South Florida's tropical climate (albeit at the very verge of subtropical) that is not favorable to Pine Siskins, we wouldn't have mangroves and tropical hardwood hammocks, and thus Caribbean island birds at their northernmost ranges. Compare a detailed Koppen Climatic map to the ranges of our mangroves and native tropical hardwood hammock species. For the most part, the distribution of the species should be U-shaped between the southern Gulf of Mexico, around the Everglades, and up the Atlantic to about Broward County, although mangroves extend farther north.
And if you really want to delve into south Florida's bird diversity further, think about the emergence of the Florida Platform, when the peninsula finally emerged. If the peninsula would have came into closer contact with the Bahamas, Cuba, or the Yucatan, south Florida could easily have it's own endemic bird species specialized to the hardwood hammocks and/or mangroves. Instead, we get the island dispersal prone species from our neighboring land masses such as Antillean Nighthawk and White-crowned Pigeons. I choose to blame the Pleistocene era and tectonics for our lack of endemics or island species breeding in south Florida. But back to where I left off, I am okay with not having Pine Siskins in Miami as long as it means we have a share of tropical species.
Lastly, something that occurred to me as I was wandering Isla de Cozumel, Quiantana Roo, Mexico in December '10 was that the climate, foliage, and geology was comparable to extreme south Florida and the Keys. In fact, many of the tropical hardwood trees were the same genus or species that we have in Florida. Brown Anoles were as prevalent as they are in Florida, as well. At some point, relating back to the formation of peninsular Florida, you have to wonder if the relative lack of biodiversity in the tropical maritime forests of south Florida are a result of empty niches. Many southeastern mammals, birds, and even reptiles have difficulty surviving in the aforementioned habitat and extend only in central Florida or the northern Everglades before petering out in density. I am not suggesting that many of the exotic species we have in Florida are not a problem, but I do believe that some that can found away from human habitation are in some way filling in empty niches where they are not competing interspecifically.
I hope this biogeographical tangent was appreciated. Honestly, initially I was only going to comment of Toe's idea of climate. And aside from my professors, I figured some of you might find it interesting or may have input for me on the matter.
And interestingly enough, the Pensacola area has only had one report of Pine Siskin at this point of the season, although it has been a good year for Purple Finch.
Alex Harper
Natural Sciences, University of West Florida, Pensacola
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