The Wild Side: The mysterious whip-poor-will
Whip-poor-wills are a fixture of Wisconsin bird life. Recognized by their distinctive call, perhaps second only to that of the loon, whip-poor-wills are readily heard but rarely seen in the Northwoods.
I remember coming up north to camp in the State Forest and hearing the birds singing in the darkness. I have had several people come to me and report that they don’t hear as many whip-poor-wills as they used to, a trend that seems to be supported by our survey information.
Whip-poor-wills are a member of the nightjar, or goatsucker family of birds. The name goatsucker came from a historic misbelief that these birds would drink the milk from goats at night. This probably had its origins in historic Old World folklore; the birds are active only after dark, and have an eerie call. If they found one of these birds, it probably looked very odd, with a very short but wide-opening bill, a large head and large eyes. These features make them look somewhat owl-like. It has very short, very small feet, pretty much useless for walking. Without valid scientific information, it is very easy for people to come to inaccurate conclusions about wildlife.
In fact, whip-poor-wills eat large flying insects like moths, which is the reason for their short, wide bills. You have probably seen their close relatives, the common nighthawks, flying around the bright lights of a gas station or stadium in an urban area. You may have thought they were big bats at first, although they made a sort of buzzy “peent” sound. They are similar in a lot of ways, but nighthawks are crepuscular, meaning they are active at dawn and dusk. Whip-poor-wills are more nocturnal, meaning they are active after dark. Nighthawks do well around people, relying on rooftops for their nesting; whip-poor-wills stay in the woods where there are less people. Both birds eat insects, migrating south for the winter. Both species also sit lengthwise along tree branches, a behavior unique to nightjars.
Whip-poor-wills do not build a nest; they lay their eggs on the ground to hatch them. They synchronize the laying of their eggs with the moon phases, meaning their eggs will hatch 10 days before a full moon. This insures that the parents will have the most available moonlight to allow them to hunt for insects to feed their chicks. Both parents work to raise the young, and the male protects the nest from potential intruders. They only lay two eggs, which has its pros and cons. With only two eggs, it takes less work to lay, hatch, feed and protect them. However, if the population drops, it takes much longer to increase numbers with such low recruitment.
Most people who approach me about whip-poor-wills feel their numbers have declined. According to the Wisconsin Breeding Bird Atlas, the bird’s numbers are lower than they were historically. Wisconsin DNR has listed the bird as a “Species of Greatest Conservation Need” due to its decline. There is very little information about this bird, likely because it is so hard to see, find, and study.
Whip-poor-wills seem to use forested, sandy areas. It appears that the birds rely on some kind of young forest for nesting. This is not surprising, as other ground nesting nighttime birds like woodcock do the same. In the Lake Tomahawk Golden-winged Warbler demonstration area, whip-poor-will numbers increased within one year of an aspen timber harvest. This might help explain why, in the span of two generations, the birds seem to be disappearing. They probably boomed after the great cutover, and have begun getting squeezed out as forests have matured across the north.
We have a well-respected secretive bird survey here in Wisconsin that relies on volunteers and public participation. There are defined routes run twice each summer. In addition, bird observations can be reported to e-bird. For more information, go to the Wisconsin Bird Conservation Initiative website, wisconsinbirds.org.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR in Rhinelander, and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.