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Sunday, December 1, 2013

Perfect Storm at STA 1E

Twice a month, first Saturday and third Sunday, Audubon Society of the Everglades leads special tours of the backroads of STA 1E located between Wellington and Loxahatchee NWR.  The special tours are arranged through South Florida WMD who manages this and many other Stormwater Treatment Areas as part of CERP.

I was honored to be a co-leader of the November 17th trip last month, and it was indeed a "Perfect Storm" of birds.  Water levels were very low, creating vast mud flats for shorebirds while still allowing deeper areas for wading birds and ducks.  The timing was such that we had a nearly full compliment of winter birds, while still retaining many lingering fall migrant species.  This convergence allowed a whopping 92 species (plus two other taxa) total for the eBird report.

We started well with many Grasshopper sparrows calling around the parking lot along Flying Cow Road at the northeast corner of the STA.  Grasshopper sparrows are far more often heard than seen by those who know the calls. (There are some really cool websites out there about bird ID, etc.  I can't find a recording of Grasshopper sparrow calls, but some really cool stuff.)  One bird sat out for most of the group of 30 or so birders to see as it rested on a chain link fence before we even started our caravan into the man-made wilds.

Once in the area, we had so many birds, I could not count them.  Purple swamp hens, now "countable" for those playing the ABA listing game.  My estimate for the day was 130 which consisted of many groups of four to eight or more birds.  Most bird numbers were gross estimates as there were so many and we were under time constraints and we wanted to make sure everyone got on the birds.  Limpkin and Snail kite were in display in numbers.  Both species are connoisseurs of Pomacea (Apple snails).  The species composition of Pomacea in Florida is undergoing a change as the larger, introduced Channeled apple snail from South America is invading more and more waterways in Florida.  We have actually seen shells of this species in the ditch outside our house.  The larger species may prove difficult for the Snail kites, which specialize in feeding on Pomacea to handle, especially as juveniles.  Limpkins are larger and have a more diversified diet, so it is less likely that they will be adversely effected.  Initially these new aggressive invaders have allowed the opportunistic Snail kites to colonize areas where they have never been seen before.  My 200th species for Hillsborough County was Snail kite which were found breeding at Medard Park by atlasers participating in Florida's second BBA.  Snail kites have nested in this area and other STA's causing staff and visitors to have to modify their activities to avoid disturbing the nesting birds which are protected by the Endangered Species Act.   We saw at least seven kites and at least 45 (!) Limpkins during the trip.

Ducks were well represented on this trip with 12 species identified.  They were quite jumpy and made us work for good views.  Most abundant, as would be expected at this time, was Blue-winged teal which are very much in favor of STA's.  The resident Mottled ducks were next up with an estimated 180 birds.  Mottled ducks are adapting quite well to an increasingly urbanized landscape in Florida.  A threat with which they are not coping so well is introgression from feral or domestic Mallard populations in Florida.  FWC has researched the issue.  Pure Mottled ducks can be hard to find in some more urbanized areas of Florida such as Jacksonville, which is a little outside of the normal range of Mottled duck, and Tampa through Sarasota area, which is not.  More "wild" areas are generally free of Mallard genes, but resident Mottled ducks are prone to movement and hybrids and backcrosses are apt to show up and breed anywhere in the state.  We only identified two hybrids among the throngs of Mottled ducks.  There could be more as the differences between the species are subtle.  I usually look for signs of white in the tail or borders of the speculum, both signs of Mallard genes in Mottled ducks.  Male hybrids or backcrosses will often show signs of black in the tail, a curl in the central tail feathers, reddish-brown breast, and iridescent green in the head.  Females are not so easy, they often show some black on the maxilla, a trait not present in pure Mottled ducks.  In addition, Mottled ducks show black at the gape.  Whether this trait shows in hybrids or not is unclear.

In among the Mottled ducks and couple of hybrids were a pair of pure Mallards.  Whether these were local resident birds, part of the feral invasion, or truly wild ducks is not clear.  It is impossible to prove that they were wild, but easy to see a big fat domestic Mallard in the wild.  Wild Mallards become increasingly rare south of Gainesville, but then again, we don't really know the true status.  I recorded them as wild on eBird, but I'm not sure if I will add them to the county list.

Other ducks of note were 20  Fulvous whistling-ducks which were scattered out among the other ducks and coots in a couple areas, 15 Gadwall which eventually gave looks to everyone who wanted, and 15 Northern pintail, which were slightly less cooperative, but eventually gave in to people's wishes.

Shorebirds were the stars of the show with two lingering Semipalmated sandpipers which will leave the U.S. by winter time, except perhaps a few in extreme south Florida, and two late, heard-only, Pectoral sandpipers which did not land where we could see them.  Dunlin, unusual inland, but usually fairly common at sites like this, were barely present with only two identified.  Western sandpiper, also unusual inland in winter, were more common with approximately 100 counted.  Ruddy turnstone, a coastal species in winter, winters in the cane fields and shores of Lake Okeechobee.  We saw two of them that morning, part of the storm.  Overall, we found 17 species of shorebirds, many of which will overwinter with the exception of the Semipalmated and Pectoral sandpipers.  Most interesting to me were the 22 Black-necked stilts, 12 American avocets, and 250 Stilt sandpipers.  Best of all was a sleeping Marbled godwit, rare inland, which stood above the surrounding birds with it's long legs.  We could not see the long, upturned bi-colored bill, but the long legs and cinnamon color was enough to ID  this fella.

This was one of those days where the species list just seemed to climb with many of those occasional species showing up all on the same say.  We were admiring the accumulation of Caspian terns and Gull-billed terns,  when both Laughing gull, and Herring gull made brief appearances.  Nearby, we had a nice cluster of American white pelicans and among them was a Brown pelican.  Brown pelicans are a coastal species that is becoming increasingly common on inland, freshwater sites.  Many of them winter on Lake Okeechobee, but most move back to the coast by the breeding season.  They are not usually seen in the STA's but this was a "perfect storm" kind of day.

The other other taxon (in the world of eBird, taxon can include spuhs, slashes, hybrids, etc.) we saw was a Great "white" heron, considered a color morph of the Great blue heron, but maybe not, perhaps we had 93 species plus one other taxon (Mallard X Mottled hybrid.)

So my next opportunity for STA 1E will be December 15, 2013 as I will be taking on the annual Paul Bithorn Exotics Trip with Tropical Audubon Society on the first Saturday of December.  Maybe once again we will have a "Perfect Storm", one can always hope.

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