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Sometime in late June or early July, an amazing and somewhat unexpected thing happened. I realized as I was driving the 45-minute route between home and Emeralda that I was beginning to view these weekly censuses as something approaching work, instead of sheer pleasure or adventure. Upon reflection, the reasons seem obvious. Florida's avifauna is at its least diverse and least interesting in summer. Between January and about early May, I was recording between 70 and 80 species on each trip - by the middle of June, that figure had dropped to just a little over 40. That drop, at least to some degree, is more apparent than real - some species that are present become harder and harder to detect, due to changes in activity patterns, and especially due to a decrease in singing by territorial passerines. I haven't heard a yellowthroat singing in 2 months, though they are certainly present in substantial numbers. Many other species behave similarly. Nonetheless, there's always something interesting happening with the wildlife of the wetlands, even if it is broiling hot, and even if it does involve the same species I've been seeing for the last several months.
|Changes in habitat structure
also contribute to the decreasing diversity. Vegetation in both wetland and
terrestrial habitats is generally explosive and often impenetrable, making observation
many species difficult or impossible. In some areas of open
water, extensive stands
of cattails (right) or other emergent
aquatics blanket the marshes. Though full of a
variety of birds, including rails, moorhens, purple gallinules, least bitterns, etc.,
unless they come to an edge, you can pretty much forget about seeing them.
the weedy vegetation bordering many of the dikes and levees becomes so tall and obscuring that many areas of my census route that provided beautiful vistas in mid-winter are now completely obstructed by dense stands of elderberry, mallows, or a variety of other herbaceous species that grow incredibly rapidly when conditions are right.
|Probably another reason for my somewhat disenchanted feelings about the area is that the mass peregrinations of snakes I was hoping for never did occur. Maybe they're there, but things are so great they don't need to move much. Who knows? I would have expected to see at least a few water snakes, racers, garter or ribbon snakes, or other generally common species crossing the roads, but for the most part, snake activity has been lacking. The cottonmouth crossing the road (left) I saw back in June looked remarkably skinny; maybe the flock of 10 or so boat-tailed grackles that were persistently following and harassing it had something to do with his, and other snakes', reticence to come out and be seen.|
Some birds have remained abundant and conspicuous, including the blackbirds. Boat-tailed grackle males (left) began a secondary period of male-male displays in June, but it wasn't as widespread as when they first begin preparing for breeding in early spring. Red-winged blackbirds have also remained highly visible, and both species began increasing in numbers dramatically in mid-summer as fledgling birds began to leave the nest. Apparent abundance of even these common birds has dropped recently, though, as they have begun their end of summer molts and are spending more time in cover.
My little friends the stilts (above), who I always looked forward to seeing at their regular spot, disappeared about the middle of June, and I haven't seen them since. I never did see any sign of young, so I'm not sure if they successfully reproduced. Young ospreys did began appearing in early summer, but in general, the number and diversity of raptors I've seen has been at a low over the summer. Even the cormorants, which are still as dependable as ever at the trusty "cormorant cypress", are less abundant in most parts of the flow-way.
Insects are diverse and abundant along most areas of my census route, due in part to the riotous vegetation. Swarms of millions of blind mosquitoes help to support huge dragonfly populations.
Butterfly diversity is quite high along the levees because of the variety of food plants available to larvae. That's a viceroy butterfly above, whose larvae feed on willows that are common in the shallow marshes.
One further reason for the apparent decline in abundance and diversity of passerines is because of changes in their behavior. During the height of the breeding season, most small passerines simply stop responding to a screech owl tape. It has always been a mystery to me why this should be so, but it's not until young birds start leaving the nest that interest in owl vocalizations begins to pick up again. That's a fledgling white-eyed vireo (who doesn't yet have the white eyes) and a northern parula above, both of which showed a mild interest in the source of the owl who was strangely calling repeatedly at mid-day. Compared to the large flocks dozens or even hundreds of wintering birds that are sometimes lured in by owl tapes, a half-dozen scraggly looking warblers, cardinals and vireos is a pretty miserable response.
One group of birds that never fails to impress, however, is the wading birds. On to them next.
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