By Joe Sebastiani, Seasonal Program Team Leader
One of my summer camp routines is to get outside and take photos of camp activities on a regular basis. On August 8th, I was out on a beautiful day and stumbled across a small flock of Chickadees and Titmice. Since early August is the beginning of songbird migration, and migrant warblers usually hang around Chickadee and Titmouse flocks, I paused for a look. Soon, I got a glimpse of a yellow-bellied bird flit through the trees. A warbler! I relocated the bird quickly and what I saw did not compute. I wasn’t familiar with this bird, but it registered in my mind from looking at bird field guides since I was young.
This yellow-bellied warbler had a faint black throat and a faint black mask around the eye. It had white wing bars, and white under the tail. It also had a golden-yellow forehead. I was pretty sure I had found a Lawrence’s Warbler, and after looking it up later, confirmed it. Lawrence’s Warbler is not a distinct species, but rather a rare hybrid that is produced by one of several parent combinations. It is a complex story, but Blue-winged Warblers and Golden-winged Warblers are very closely related. They hybridize freely, and normally produce a hybrid called a Brewster’s Warbler, which is white bellied with a black eye stripe. A Lawrence’s Warbler is product of a more complicated pairing summarized this way by the Peterson Field Guide to Warblers, “Lawrence’s Warbler is produced by pairings between a “Brewster’s (existing hybrid) and a Golden-winged Warbler that carries the recessive gene for yellow underpart color; or a pairing between a “Brewster’s and a Blue-winged Warbler that carries the recessive gene for the black-mask and throat; or a pairing with two Golden-winged Warbler carrying the recessive gene for yellow underpart color (1 in 16 chance); or a pairing of two hybrid “Brewster’s Warblers”.
Unfortunately, populations of the straight-species Golden-winged Warbler, which nests in the Appalachian Mountains and around the Great Lakes States, are losing ground. They are disappearing due to loss of their early successional habitat requirements for nesting, but to make matters worse, Blue-winged Warblers are swamping their genetics by hybridizing with them. The result has been a steady decline in Golden-winged Warblers. Sightings like the Lawrence’s Warbler I found at Ashland, are a reminder that species divisions can be a bit blurry sometimes, and the notion of a species doesn’t always fit into our neat and tidy human definition, even for two birds that are distinctly different in appearance.
In Delaware there are records of this hybrid from 1932, 1979, 2006, and possibly another record that I do not have a date for. That makes this the 4th or 5th record of this hybrid to be found in Delaware. This rare and unusual bird was exciting to find and a challenge to photograph. You never know what you will find on a nature walk, and any average day can hold the biggest surprises.
If you are interested, there is a Fall Warbler Preparation program happening at Ashland Nature Center this Saturday, 1-4pm. It is free for members of the Delaware Nature Society and $5 for non-members. Please call 302-239-2334 email email@example.com if you would like to attend.