Tues 9 May 2017
Sunday 7 May 2017 was the annual Charleston Spring Bird Count. It is essentially a spring version of our annual Christmas Bird Count using the same 15 mile diameter counting circle and the same subdivisions for counting within that circle. As I recall hearing, the count circle was placed where it was precisely to include Bulls Island. We've always divided the island into north and south halves, each counted by different teams of birders. For several years Felicia Sanders and Mary Catherine Martin have counted the north half of Bulls, sometimes with the assistance of other birders, and Starr Hazard has helped me count the southern half of Bulls, also sometimes with the assistance of other birders. This year just we four covered the island and the marshes between the landings, with special thanks to both Felicia and MC for the boating arrangements.
Unfortunately for the shorebird counting, the noon low tides on Sunday left the shorebirds scattered away from their usual high tide roosts. Felicia and MC did however discover many Least Terns incubating eggs right on top of the new, uncompleted dike crossing Jack's Creek. While I had noticed that numbers of skimmers, gulls, terns, and shorebirds were resting along central lengths of the new dike I did not know that the Least Terns were nesting there. Here's hoping that the Least Terns have a successful nesting season on that dike. Maybe other terns and skimmers will likewise use the dike top for nesting in a few weeks.
Starr and I enjoyed relaxed time to bird the picnic grounds and lawn at the Dominick House, one of my favorite birding spots on the whole coast line. I always anticipate these counts that allow me to focus on areas of Bulls that I don't have the luxury of birding during my biweekly waterfowl/shorebird surveys. We heard and saw several Least Bitterns (always a special treat), several Anhingas, numerous Tricolored Herons and Green Herons (mostly as flyovers), a Wood Duck, Yellow-billed Cuckoos, Common Nighthawks, Summer Tanager, Blue Grosbeaks, Indigo Buntings, Bobolinks, and Orchard Orioles. Always a special treat, we saw three Bald Eagles; one mature eagle was standing right on the low-tide front beach.
Unfortunately there was almost no activity at the rookery spot well south along Mills Road. We saw only a pair of Green Herons that flushed from there and saw no nests at all. For years the egrets and herons have used that site as a rookery. The site appears to retain several of the bare, "leggy," dead trees that held the stick nests in prior years and the water level appears to remain high. The nests just aren't there right now.
We got to talking about Spotted Sandpipers (SPSA) and how it was nice to see them in their alternate (breeding) spots for a short time before they migrate away. Turns out that SPSA are much more widespread in their breeding range than any other North American sandpiper. Their breeding range spans the entire width of North America from roughly Kansas northward about to the tree line in the North American arctic (which is primarily where all other migratory sandpipers migrate to for their breeding). Additionally SPSA are polyandrous, i.e., one female will mate with more than one male, a very unusual mating system for birds. This leads to sometimes vigorous competition between females for limited males who, by mid-season, are too busy incubating eggs to be available for mating. In SPSA the female will lay a clutch of up to 4 eggs (one egg weighs approximately 20 % of the weigh of the female bird), leave those to the incubation care of a male, then move on to mate with another male to produce another clutch. This behavior seems to come with costs of frequent emigrant movements due to reproductive failures, relatively short life expectancy (3.7 years), high numbers of eggs laid (into multiple nests with multiple males), and low nest success.
P.S. Information presented on SPSA comes primarily from: Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988 The Birder's Handbook: A Field Guide to the Natural History of North American Birds. Simon & Schuster Inc.: New York. p. 131.
Tues 16 May 2017
Julie Mobley joined me yesterday for the waterfowl/shorebird survey. We had the luxury of our own F&WS boat so weren't committed to any particular time schedule but our own. We put that to good use on the ride out to Bulls when we stopped at one point to observe a few shorebirds; while drifting in the tidal currents and wind we heard the distinctive "water sizzling on a hot skillet" sound of a Nelson's Sparrow. I quickly killed the motor and heard repeated calls from the sparrow hiding in the Spartina. We never had a good look at the bird, but the repeated call was so distinctive that it became an easy identification. That may have been the first time that I've ever heard a Nelson's Sparrow. Pretty cool beginning to our outing.
Good news for the Least Terns found nesting on the new dike in Jack's (read about their discovery above under 9 May 2017 section). Significant lengths of the new dike have now been closed to any access to allow the Least Terns, and hopefully other terns, gulls, and skimmers, to nest. In a fortune of good timing, the construction shovels appear to have been removed from the island very recently. I'm hopeful that this means the dike construction is nearing completion.
Shorebirds continue to hang around the island, many in full-on alternate (breeding) plumage including Black-bellied Plovers, Wilson's Plovers (nesting on Bulls, we saw two juveniles), many Spotted Sandpipers, many Red Knot (uncommon on Bulls; the 43 that I tallied is likely the highest count that I've ever had on Bulls), Sanderling, Dunlin, and Semipalmated Sandpipers. Additionally we had a Stilt Sandpiper, a Black Tern, a trio of Black-bellied Whistling Ducks, a few Common Terns, a couple of Caspian Terns, and many Sandwich Terns (47, a very high count).
Anecdotal observations by differing SCDNR folks, consistent with my own observations, are that the usual May spring tide influx of horseshoe crabs laying eggs, a favorite food of many shorebird species (especially Red Knots), hasn't been happening this year, at least not yet. Rather than seeing scores of horseshoe crabs coming ashore I've seen few to none. I've noticed that many fruit and nut trees only produce decent crops either biennially (i.e., every two years) or triennially (i.e., every three years). Makes me wonder whether horseshoe crabs exhibit similar multi-year cycles in their mating and egg laying. If anyone has knowledge or thoughts on this I'd appreciate hearing from you.
The most unexpected sighting was a flyover Sandhill Crane while we were on the North Beach. It soared in off of Bulls Bay directly overhead showing it's red crown. New species for the survey (I think) and new eBird species for Bulls Island!
We tallied 66 species on the island and 72 species on a beautiful day's outing. Combining my Sun 7 May 2017 Spring Bird Count (read about that above) and this waterfowl/shorebird survey gave 93 species! Our two main eBird checklists for Bulls are available online at:
https://ebird.org/ebird/view/checklist/S36653885 (Spring Count)
https://ebird.org/ebird/iss/view/checklist/S36911111 (waterfowl/shorebird survey)
Cathy Miller sent me a link to a story about BO:X,g, a.k.a., Old Man Plover. Since you made it this far into this blog posting, I'm going to share it with you:
Looking ahead at the tidal calendar suggests the following dates to consider for our next survey:
Sun 28 May 2017 5.2 ft high tide forecast at 10:42 AM
Mon 29 May 2017 5.1 ft high tide forecast at 11:41 AM