Saturday, August 30, 2008

Fouteen species made up the catch...

This day made me begin to get excited about fall migration season. Birds picked up today with a calm morning to allow for some migrants to drop in. It's not much but a 36 bird day after less than double digits for a day seemed like things were looking up. Fourteen species made up the catch including five recaptures. Seven warblers were captured today (Black-throated Blue, Common Yellowthroat, Ovenbird, Magnolia, Chestnut-sided, Wilson’s, and Mourning). Yes, I realize the best warbler has been seen on the Magee Bird Trail but I have yet to see one Blackburnian. I am glad others are getting to enjoy the birds. Yes, they are seeing multiples of Blackburnians. My time will come.

One of the attractive warblers in fall is the Chestnut-sided Warbler. Their basic plumage is quite beautiful or handsome depending on what sex it is. Even if you cannot see any chestnut on its sides see if you can see the upper tail coverts. The males will have very distinct black centers to the upper tail coverts. You are already gazing at the bird to identify it, why not see if you can tell what sex it is? Challenge yourself!

Another challenge is the Baltimore Orioles at this time of year. Unless you look closely you may be calling the Baltimores you see- females. Well, the immatures look female-like—Hmmm what would be the advantage of that? Survival tactic, it is best to blend in. If you look at these photos can you tell which is an adult female, immature hatching year male, and an unknown immature (hatching year)?

You can actually tell by just looking at the heads of these birds. First look at the beak color. An adult Baltimore will have a slate gray bill with the upper mandible being slightly darker than the lower. The bill looks that way on an adult male too but who looks at the bill with the brightly colored black and orange bird? The immatures have a lower mandible that is not gray but flesh to pinkish color more so towards the base of the bill. The bill has not matured or reached its hardened state. By spring the bill will not be a characteristic to use for aging but it works in the fall at this time and latitude. This bill coloration difference occurs in many if not most of immatures of the same species. It is very apparent with adult and immatures of Yellow Warblers. Okay back to these pictures. The immature pictures you will see some black coming in on the face of one. That bird you can sex as male. The other one has to go as unknown at this time. I always make notes because there are some that I really think could be females because of their pale coloration even at this date. A few of these birds will return to this site next spring and can be compared with my notes and what the bird is in its alternate plumage. Unfortunately not many come back to this same exact location for much of a sample size to amount to anything but anecdotal information. Wing chord length does not help because of the great overlap in measurements of both sexes.

All sorts of things to ponder… Enjoy!

No comments:

Post a Comment