Sunday, January 4, 2009

Aurora Reservoir Gulls

January 3, 2009

Richard Stevens:

In the morning I went over to Rocky Mountain Arsenal (Adams County). It was a useless attempt to find the Tundra Swan reported Thursday. I circled Lake Lenore but most of it was frozen (small open area at the western, closest end). The eastern end where the Tundra Swan was observed was completely frozen.

It took an hour to circle the lake and make sure there were no birds. Back at the western end, about 15 Common Goldeneyes and 14 Common Mergansers were among a dozen Ring-billed Gulls, one or two California Gulls, and three Herring Gulls.

Winds were 22+ mph, gusts to 34 mph; temperatures in the upper 20s. I think my anemometer froze; I did!

I met up with Jerry Petrosky and Bill Cryder after Noon. We spent the rest of the day walking the 7.8 mile bike path around Aurora Reservoir.

Again many gulls were below the dam. Unfortunately none of the uncommon gulls were here. The southeast corner was best, but required a 4 mile hike to get there.

Here we found a Tundra Swan (could it be the Rocky Mountain Arsenal swan?). Two adult Lesser Black-backed Gulls stood off mm 4.0. The strange Gull was with many Ring-billed Gulls, a few California Gulls, and several dozen Herring Gulls off mm 4.5.

Land birds including sparrows were really scarce. One flock of American Tree Sparrows (5) at mm 1.5. A couple of Song Sparrows south of the marina.

Raptors included 2 Red-tailed Hawks, 1 American Kestrel, and a female Northern Harrier. The new construction along the northern end of the reservoir is not going to help the birding. Someday Aurora Reservoir will be another Cherry Creek Reservoir.

Jerry Petrosky, Bill Cryder and I found and photographed an interesting Gull at Aurora Reservoir Saturday. It was slightly larger or similar in size to the nearby Herring Gulls. This bird was quite far away from us. I digiscoped it, but light was terrible except for a short time. The legs were pink and at times looked bright pink (again the light). The mantle was dark, too dark most of the time to be a Western Gull (again bad light?) but at times looked lighter than a Lesser Black-backed Gull. It probably was a small Great Black-backed Gull, but wish we could have observed it under better light.

I am not suggesting that anyone rush out there. The Gull population changes throughout the day as the gulls fly back and forth to DADS (Denver Arapahoe Disposal Site. aka. landfill). I have sat out there for eight hours and never observed the same gulls more than once or twice.

Will not have the chance to go back out there until Tuesday. I sent photos to a "Gull expert" in California. Hopefully he will shed "light" on the bird. If there is a best time to see most of the gulls, 11:30 to 12:30 seems to be when many gulls fly back from the landfill; other days this is not so much true. The interesting gulls today were at mile marker 4.5 (southeast corner of the reservoir).

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