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The edge effect, as ecologists call it, refers to the observation that areas where two or more different habitat types abut are often surprisingly species rich compared to either of the habitat types by themselves. Probably because of the large amount of edge in the flow-way between open marsh habitats and more closed, structured habitats such as hammocks and corridors of canopy trees, there is an abundance of small wintering passerines in the area. Small passerines are often challenging to the birder because of their skulking nature, and especially challenging to the bird photographer because you have to be so close to them to make a reasonable image, and when little birds are that close to a potential predator, they don't sit still for very long.
Mixed species flocks of wintering insectivorous birds are thick in the area, especially around the margins of the marsh habitats where they meet forest or brushy borders. One of the most common of the wintering species is the yellow-rumped, or "myrtle" (eastern subspecies) warbler. The easily recognizable metallic chip of these birds is one of the most characteristic sounds of the edge areas during winter.
Second in abundance to myrtles are blue-gray gnatcatchers. Though these active, inquisitive little birds breed in our area, most of the birds here in winter are probably migrants from further north. One of the most surprising observations I have made to date occurred on March 11, when I saw or heard not a single blue-gray gnatcatcher on my entire census. I had been seeing or hearing between 20 and 50 birds per census on each week previous. I'm assuming this huge drop represents migratory birds leaving the area.
One of the methods I use to census small birds is playback of a taped screech owl vocalization. Many small birds will seek out the owl to "mob" it, and even if they find no owl, they will stay in the vicinity of the vocalization for several minutes in a highly agitated state. Gnatcatchers are one of the most responsive and inquisitive birds in these mobbing flocks.
The abundance of water in the surrounding habitats certainly buffers the environment to some degree, and prevents wider fluctuations in air temperature in the immediate vicinity. Hatches of aquatic insects may also be a major source of prey for insectivorous birds, especially those that feed on flying insects nearly exclusively, such as the tyrannid flycatchers. Eastern phoebes (below left) are thick in the area, and on two censuses in March I was fortunate to see an Ash-throated flycatcher (below right), a western species that on rare occasions somehow finds its way into Florida.
A variety of other insectivorous passerines also show up with varying frequency in the area. A few of these are seen below.
This is a common yellowthroat, another skulker. They are heard more easily than seen, especially in late winter when the males begin singing their "witcheri-witcheri" song.
Another notorious skulker is the house wren (below left), a wintering bird that stays hidden the majority of the time. In the middle is a mockingbird, and the little tail-wagger on the right is a palm warbler.
My main focus at the Lake Griffin Flow-way, however, has been birds that are more directly associated with the marsh and wetland habitats. On to them next.
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