Lesser Nighthawk

Aside from Raptors, my favorite group of birds are the nightjars. The nightjars are large-headed, large-mouthed nocturnal birds that are evolutionarily somewhere between owls and swifts. There are eight species found in the North America. They are typically seen flying low over open areas in search of flying insects in the evening or early morning. Nightjars are also often seen sitting on dirt or gravel roads. The Common Nighthawk can be found throughout North America and as its name implies, is fairly common. However, here in the desert Southwest, the more numerous nightjar is the Lesser Nighthawk. The Common Nighthawk is slightly larger than the Lesser Nighthawk, but the nest way to tell the difference is that the white wing bar on the Lesser Nighthawk is closer to the wingtip than the white wing bar on Common Nighthawks.

Lesser Nighthawk sitting along a dirt road in Imperial NWR; photo by Anna Fasoli.

On my way out to survey for cuckoos every morning before the sun comes up, I get to see lots of Lesser Nighthawks. Unfortunetly this morning as I was driving to a survey plot, a nighthawk flew across the road and was hit by the front of the car before I even had a chance to react. I pulled over and ran back to see the bird, and sadly, it had died. One of my coworkers also had spotted another dead one along the road a few days ago, so between the two deceased Lesser Nighthawks we collected, I had taken enough photos to write this blog explaining how to tell the sex of them. One of the birds is a after hatch-year (AHY) or after second year(ASY) male and the other is a hatch year (HY) or second year (SY) female. Using photos I have taken, I will try to explain how I came to that conclusion.

This photo shows the top of the wing of an HY/SY nighthawk. Note the vertical white bar across its primary feathers. Also note the minimal cinnamon coloration on the tips of the primary and secondary feathers.This photo shows a AHY/ASY bird; note the lack of vertical white bar across its wing and also that the cinnamon-colored horizontal bars run much farther across its wing than they do in the above photo of the adult bird. Also note the cinnamon coloration on the tips of all the primary and secondary feathers.

The easiest way to tell age and sex is to focus on the vertical wing bar that runs across the Lesser Nighthawks primary feathers. The amount of cinnamon coloration on the wingtips can also be helpful in aging and sexing, however the presence or absence of a white wing bar is much more obvious and exact.

This first photo shows a close-up of the wing bar on the HY/SY nighthawk. Note that the wing bar is white and runs from one feather to the next seemlessly.

This photo shows a close-up of the wing bar on a AHY/ASY Lesser Nighthawk. Note that the wing bar is a cinnamon color rather than white and that it does not seemlessly transition from one feather to the next.

So now we know the we have a AHY/ASY nighthawk and a HY/SY nighthawk, now how can we tell more about sex? Take a look at the next photo, highlighting the white pattern on the 7th primary feather (also known as p7).

The fact that this white pattern (inside the red circle) is white and covering across most of the feather shows that this bird is a male. The white pattern on the p7 of a female would be much smaller and not as cleanly white. Like I mentioned, the white pattern is across most of the feather, but not covering across it completely so that it basically cuts off the black coloration from the tip of the feather and the rest of the feather. Also the small bit of cinnamon coloration at the very tip of this feather is another indicator that the bird is a HY/SY bird and not a AHY/ASY.

This photo shows the p7 of the HY bird. Note that the pattern in the red circle is not white. This immediately tells you that the bird is a female. Also, because the pattern is covering a good majority of the way across the feather, it is a AHY/ASY bird and not a HY/SY bird which would show a small amount of patterning.

Another way to sex Lesser Nighthawks is to look at the subterminal band across their tail. If the band is white, then it is a male. If the band is a lacking or buffy-white, then it is a female. The subterminal band on the HY/SY bird was white, therefore adding more evidence that that particular bird is a male. As for the other bird's subterminal band, it didnt have one....its tail band looked no different than any other marking on its tail, therefore its for sure a female. Unfortunetly I didnt take photos of the bird's tail bands....

So now that I confused everyone who plans on reading this (including myself), we have concluded that one bird was a AHY/ASY female and the other was a HY/SY male. The reason that we cannot go further and say exactly what age the bird are is because currently there is not enough research on Lesser Nighthawks to make that conclusion, but I think we narrowed it down well enough.

By the way, the live Lesser Nighthawk in the photo at the top of the post is a female, because it doesnt have a white tail band and its white wing bar should be evident in that position if it were a male, and it isnt, so once again, that bird is a female.

References:

Pyle, Peter. Identification Guide to North American Birds: A Compendium of Information on Identifying, Ageing, and Sexing "near-passerines" and Passerines in the Hand. Bolinas, Calif.: Slate Creek, 1997. Page 100 - 103.