Thursday, May 23, 2013

Bulletin 175 - odds and ends from the spring

There were a couple of interesting and rare birds  at the end of migration.

The first I saw with my buddy from NYC on Sunday April 28th at the Texas A&M woodlot on Galveston Island. It was a nightjar that flushed up from close to the ground and landed on a dead fallen tree. We observed it closely for about 20 minutes as it flew back and forth between perches. The 3 nightjars here in Galveston, are the Common Nighthawk, Whip-poor-will (WPW) , and Chuck-will's-widow (CWW). I had been hoping to find a Whip-poor-will to photograph. The Common Nighthawk has very long wings that extend beyond the tail. The other 2 have shorter wings and the tail extends to or beyond the wings. This bird became an ID challenge.

Here are my first 2 photos of the bird perched, both showing the tail as longer than the wings.

Also, we clearly saw that when it flew, it had a buffy stripe across the wing near the tip. I knew that Common Nighthawks of both sexes, have a white stripe across the wing. So both of these marks, the shorter wings and no white wing bar, led me to believe it wasn't a Common Nighthawk. I have photographed several CWWs and they have a very dark brown throat. Obviously not our bird. So by default, I was left with an ID of a Whip-poor-will. I have never seen them flying, so I didn't know what they looked like aloft.

I posted the images to Texbirds, and had a few responses, but the important one was that this bird is a Nighthawk. Only in Sibley can you find the field mark shown of the white feathers under the edge of the wing at the shoulder when perched. This bird clearly had those white feathers at the shoulder. This IDs the bird as a nighthawk.

So I was disappointed that I didn't have a WPW photo, but what was this bird? I want back to the same place after work the next day on Monday 29th and fortunately, he was still there and I had a chance to look at it again. Definitely, it had a buffy wing bar. The only other nighthawk possible is a Lesser Nighthawk. This bird is a bird of the south Texas to south Arizona. It is listed as an occasional vagrant here, but I can only recall a couple of mentions in my 20+ years birding here. The female Lesser Nighthawk (Chordeiles acutipennis) does have a buffy wing stripe and the male has a white one. Bingo! Also, the Lesser Nighthawk has a tail as long or longer than the wing tips.

The other interesting thing was that a Lesser Nighthawk had been reported at the west end of Galveston Island 2 weeks before. The next week, one was positively IDed at LaFitte's Cove in the center of the island. Then I had this bird at the extreme east end. The following week, a Lesser was found at High Island, a further 40 miles east along the coast. It appears that this bird was moving slowly up the coast.

The other important field mark is small buffy spots on the primary wing feathers of a Lesser. This can be seen in this photo.

Lesser Nighthawk - female
Here is a Common Nighthawk (Chordeiles minor) for comparison. Notice the white patch on the primary feathers, but there are no buffy spots at all.

Common Nighthawk
So this was a great find. I have never seen a Lesser Nighthawk perched before as they normally roost on the ground. I only had a couple of photos in the air.

The other rare bird was the European subspecies of Whimbrel (Numenius phaeopus) found by an astute birder on Bolivar. This distinct subspecies (N. phaeopus phaeopus) has a white back, rump and tail. The local subspecies (N. phaeopus hudsonicus) is all brownish. This subspecies is a rare visitor to the Atlantic states (perhaps 6 records). There is also a Siberian subspecies that has a few records for Alaska and also has the white back and rump. This is the first Texas record of this subspecies.

The Whimbrel has already been proposed to be split into 2 species, Hudsonian Whimbrel and Eurasian Whimbrel. The British Ornithology society as well as the International Ornithologists' Union are both considering this split. So it is neat to have the bird already recorded prior to the split.

Here is an article I found discussing the proposed split and why some of these similar species in North America and Eurasia eventually drift apart genetically.

So here is the bird. The curved bill and striped head indicate the Whimbrel. The white back, rump and tail are obvious.

Eurasian Whimbrel
Large owls often eat small rodents and as they eat them whole, they regurgitate the fur and bones in a lump called a 'pellet' after the digestive process. I found a pile of these pellets at a spot in LaFitte's Cove. They appeared like a glob of mud. However, a close up shows it is mostly fur.

Owl pellet
I pulled it apart and sure enough, there were numerous small bones.

Owl pellet
Lastly, we had a pleasant surprise at home when we first unfurled the umbrella over the table on our patio in mid April. A tiny bat was found roosting inside the umbrella. It flew off with the commotion of the party and being exposed, but he returned the next morning. He has been present ever since, now going on 6 weeks. I have named him Mr. Ding.

I dug out my mammal book to try and ID the species and also looked up to see what species were recorded in the Houston area (11 species). I measured him while he was asleep and found him to be only 2" long. I took some photos, as one of the important features that help in bat ID is the shape and size of the ears. My diagnosis was Tricolored Bat (Perimyotis subflavus). It was formerly known as the Eastern Pipistrelle. It is named for the fur which is black at the root, lighter brown in the middle and dark at the tip. I sent the photos to Bat Conservation International in Austin and my ID was confirmed.

So here are 3 photos of Mr. Ding.

Tricolored Bat

Tricolored Bat
And lastly, a face on photo to show his ears clearly. The ears are rounded. The tragus (the small cartilaginous flap in front of the ear canal) is short and rounded.

Tricolored Bat

Male Tricolored Bats are solitary in the summer, while the females roost together in small colonies of 10-30 animals to raise their pups. It will be fun to see how long he stays with us and whether he returns next year, as the life span is up to 15 years.

This is the first bat species I have been able to photograph, as well as being a life mammal.

Happy birding and photography,

David McDonald

photos copyright 2013 David McDonald

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