Bald heads reveal dinosaur ancestry

I took the feeders down this past spring to keep the bears away and instead have been scattering black oil sunflower seeds on the broad railing and picnic table on our porch. In the summer I was doing it at dawn, but now, with the shorter days, it's closer to 6. As soon as I step out on the porch I hear the Chickadees calling to each other, announcing that breakfast has arrived. They are landing even before I am finished. In a nearby tree I hear the resident Cardinal alerting his mate. They are a little bit more cautious and wait until after I have gone back inside.

The minutes of peaceful feeding usually end with the noisy arrival of a family of Blue Jays. They are molting in late August and every year one or two sorry-looking individuals show up bald - with few feathers, or may be just a stubble on their heads. Fortunately that's only a temporary state lasting about two weeks until the feathers have regrown.

Although adult, they often look immature because their large eyes are more characteristic of chicks:

Others have more reptilian features:

The naked heads remind us that their ancestors are dinosaurs, not mammals, and that their closest living relatives are the crocodiles. They usually reach maturity within 12 weeks, but retain the large eyes characteristics of juvenile dinosaurs.

In a study published in the journal Nature on 5/27/12 examining this curious fact the authors conclude that 
        "We have provided a powerful new example of how heterochronic changes,       paedomorphic" (retaining juvenile characteristics) "and peramorphic" (early development of adult characteristics) "were crucial in the origin and evolution of birds. We further demonstrate that these changes were driven by an extreme degree of elaboration in vision-associated areas of the brain that parallels the olfactory elaboration of mammals, and possibly by the evolution of the face into a precision grasping mechanism as the hands were co-opted for flight."

There is a very readable illustrated summary of the study in ScienceDaily:  Evolution of Birds Is Result of a Drastic Change in How Dinosaurs Developed 

Late Migrants

I was walking with my dog along the West River Trail starting at the Dummerston end and ran into a mixed flock of Blue-headed Vireos, Yellow-rumped Warblers and Chickadees.

On my way back they had all moved on. There were lots of sparrows though, mostly white-throated. I am not sure what this White-throated Sparrow was eating.

Here are some photos of other recent fall sightings.

Scarlet Tanager, probably adult female

Red-eyed Vireo

Common Yellowthroat, probably first winter male

Wilson's Warbler, adult male

Happy fall birding!

Common Nighthawk Migration

For the past couple of weeks I have given supper short shrift  -  quick meals out of the freezer or whatever leftovers I could put together -  because during the second half of August supper time is when the Common Nighthawks pass through on their fall migration. Every evening for the past several years Vermont birder Don Clark of Grafton has has been observing the migration at Westminster Station near the Connecticut River, a perfect wide open location with good views in all directions.

Other birders, both local and from across the state, have been joining  him in spotting and counting the passing migrants for the annual record. They fly in small flocks, starting as barely visible dots on the distant sky, then turning into tiny ciphers fading in and out of view, and then suddenly they are right overhead, flashing their white wing patches, with little time for the lens to lock onto the target. When actively feeding their flight is erratic, banking and curving, suddenly veering off into a different direction. And before you know it  the opportunity to catch a good shot has passed. I found it helps to set my camera on continuous autofocus, have a fast memory card and then fire away until the buffer is full at about 100 shots, if set on JPEG Fine, or 19 when shooting RAW.

Male Nighthawks are distinguished by a white sub-terminal tail band which is absent in females and juveniles. 

I am including these two shots, the one above and one below, because the legs are extended. They weren't coming down to land, but maybe they did so for some other maneuver that escaped me. 

The birds are often flying with their huge mouth agape when hawking flying insects, but  I only caught two of them doing so.

I apologize for these blurry shots, just using them to illustrate this behavior.

Common Nighthawks are long distance migrants from continental North America, usually along river valleys and lake shores, to their wintering quarters in South America. They have been listed as critically imperiled in the New England states.  In the past, migratory flocks often numbered in the 1000's  According to Don Clark the highest number this year at Westminster Station was 641 on 8/22, but on most evenings the counts were much lower, often in the 100's or low 200's. 

Here's a link to a  video featuring  recordings - the peenting nasal call and the boom made by the wings when the bird is diving - narrated by Macaulay Library curator Greg Budney. Great photos too, much better than mine.

Finally on the last day, just when the numbers of passing Nighthawks had tapered to almost nothing, we were treated to two Bald Eagles circling above.

Happy Fall Birding!