Tuesday, December 14, 2010

Tullytown, Pennsylvania - Gull Nirvana

Today I poked around one of the less widely known of the varied ornithological treasures of the Delaware Valley – Tullytown, Pennsylvania. Tullytown, along the Delaware River in southeastern Bucks County, PA, is home to several gigantic landfills that service the greater Philadelphia area. The landfills attract one of the largest concentrations of gulls in eastern North America – hundreds of thousands are present most winters. Since there isn’t much available on the web to help those in the Delaware Valley seeking a fix to the crippling pathology that is Larophilia, I’ve put together a bit of information that might be useful.

Tip number one – don’t go on a Sunday. It seems that active use of the landfills shuts down on Sundays and there is much less gull activity in the immediate vicinity. All other days of the week seem to be fine.

Like many landfills that attract gulls, satisfactory viewing in the Tullytown area can be problematic due to access control and security issues. Access to the landfills and most of the adjacent ponds (including the Van Sciver Lakes) is pretty much out of the question unless you become a member of Waste Management’s Penn Warner Club. However, there are a couple of publicly accessible sites that can provide good views of loafing and bathing gulls. Both of these can be located easily using the search function on Google Maps. One is Franklin Cove, an outpocket of the Delaware River tucked in between an industrial strip in the town of Tullytown and one of the giant mountains of trash on Waste Management property. Only a few years ago, a nice loafing flock of several thousand gulls could be expected on the grass at Franklin Cove in the winter months– since the landfill site immediately adjacent to the cove is now inactive and trash dumping has primarily moved a bit north to the G.R.O.W.S. sites, fewer gulls use the cove now, though it is still a viable option and often holds a few hundred loafing gulls (and is also good for Great Cormorants).

The far better choice for secure and legal gull viewing in the Tullytown area is the Falls Township Community Park. Here, thousands of gulls cycle through the ponds to bathe and loaf on the shore or on the adjacent sports fields. Today there were in excess of 7,000 large gulls on the soccer fields at the park, with lots of turnover through the middle of the day. A scope is useful since large flocks of gulls, like most birds, are not terribly approachable when they are resting.

Herring, Great Black-backed, and Ring-billed Gulls make up the vast majority of the Tullytown gulls through the winter, though large flocks of Laughing Gulls can also accumulate during the warmer months. Lesser Black-backed Gulls are plentiful, as Bucks County is one of a few North American strongholds of this Old World gull (counts of 400+ have been recorded on lakes in the northern part of the county). Today I saw at least 65 Lesser Black-backed Gulls around various spots in Tullytown, and I only scanned a small fraction of the birds present in the area. Iceland and Glaucous Gulls are always present in small numbers in winter, though Icelands usually outnumber Glaucous (often a ratio of greater than 5:1 Iceland: Glaucous). Today I saw 4 “Kumlien’s” Iceland Gulls and 1 Glaucous Gull – numbers of these Arctic “white-winged” gulls should continue to grow through the winter. Thayer’s Gull is also annual, but is much rarer than Iceland Gull and should be diligently documented if encountered.

Several nice gull rarities have been recorded around Tullytown, including California and Slaty-backed Gull, and this site is highly likely to produce one of the next species for the PA state list (I predict these will include Glaucous-winged Gull and Black-tailed Gull). Hybrids are fairly regular, and a concerted gulling effort will often turn up several hybrid gulls in a single day. The most commonly encountered hybrids in the area are Glaucous x Herring (or “Nelson’s” Gull) and Lesser Black-backed x Herring. Today I saw two different presumed Lesser Black-backed x Herring Gull hybrids at Falls Township Community Park – a photo of one is below. With Lesser Black-backed Gulls expanding their population explosively in the last half-century (accompanied with a large breeding range expansion in Europe extending west to Greenland), I think we can expect to see more individuals of this hybrid combination in coming years. Though it is unknown if the “Herring” parents of these hybrids represent American/ Smithsonian Gulls or European Herring Gulls, I think it is overwhelmingly likely that they are of American origin.

Gulls can be enjoyed by all types of birders, but they almost certainly will help take your skill to another level if you are persistent (or you might just get a headache and go home to watch football). One of the greatest lessons I’ve learned while birding was taught to me by Herring Gulls – individuals within a single species can show DRAMATIC variation. Learning the variation within a common species can really enlighten more complicated identification problems. Good luck!

The large gull at center is likely to be a Herring x Lesser Black-backed Gull hybrid. Actually, I'm fairly certain that's what it is, but it is usually prudent to hedge visual-only identifications of hybrid birds with words such as "presumed" and "probable" because of the imprecision of visual diagnosis of hybrids. The bird had upperparts that were intermediate in shade between Smithsonian/ American Herring Gull and Lesser Black-backed Gull, fleshy yellow legs, and intermediate body shape between the two suspected parent species.

This pigment-challenged (check out Tony Leukering's article elsewhere on this blog to figure out the correct terminology) Ring-billed Gull was just south of Tullytown in Bristol today.

"Kumlien's" Iceland Gulls are an expected treat in the greater Tullytown area - most are first cycle birds such as this individual, which is typical for a site near the southern edge of an Arctic gull's wintering range. The bulk of the adult age classes typically don't migrate as far south - sites in the northern Great Lakes, New England, and maritime Canada see many more adult Icelands than we get in the Delaware Valley.

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