Sunday, June 17, 2018

The Phoebe and the Cowbird

"Mom!  Any old mom, I'm hungry!
Linda Bower sent me a note along with a link to a You tube video she posted.
"A cowbird parasitized a phoebe nest that is located by my front porch. Phoebe parents are rearing a cowbird instead of their own babies. I'm disappointed and it is hard to watch the insects from my yard and tiny pond (dragonfly larvae) getting eaten, but this cowbird chick is as cute as it can be."
First, I would encourage you to watch her video with the perfect musical pairing of Mozart's Eine Kleina Nachtmusik.

The highlights for me were the recognizable insects and the size of them that the cowbird chick managed to stuff down.  In one late sequence, the chick, which we named Mozart, has a big wad of butterfly apparently stuck while the phoebe tries to ram an additional insect into its craw. 

Serving seconds

In addition to seeing the diversity of insects the phoebe collects, you will get a close look at the nest sanitation habits of the bird.  Mozart extrudes the fecal sac when fed or sometimes even before.  Frequently it backs up over the edge of the nest to drop it down and other times the phoebe collects it as it comes out.  In case you missed the recent fecal sac description, I repeated it below.*

Until now I have never found anything to love about brown-headed cowbirds aside from their melodic liquid call, a musical gargle. They are brood parasites, leaving their eggs in other birds' nests where the new mother doesn't recognize them and raises the cowbird as her own.  Since the cowbird egg can hatch earlier and the baby is larger, it hogs the adoptive mothers attention. The cowbird chick may even attack the nest mother's own eggs.

This parasitic strategy was important when cowbirds followed bison on the prairie, harvesting insects, and were on the move daily without time to build a nest.  Many prairie bird species recognized their eggs and tossed them out.  Now that they are no longer migratory, cowbirds have moved into our urban areas where there are close cropped grasses, cropped by lawnmowers rather than bison.  Here they find nests of bird species that weren't prairie species. These naive birds aren't familiar with the dastardly habits of the cowbird and frequently lose their nestlings to the parasitic cowbird young that they don't recognize.

I dare you to go back and view the last of the video again.  Linda's timing of Mozart's "final movement" at 5:32 is absolutely brilliant!

*  "A fecal sac (also spelled faecal sac) is a mucous membrane, generally white or clear with a dark end, that surrounds the feces of some species of nestling birds.  It allows parent birds to more easily remove fecal material from the nest. The nestling usually produces a fecal sac within seconds of being fed; if not, a waiting adult may prod around the youngster's cloaca to stimulate excretion."  Wikipedia

Linda referred me to this article if you are tempted, like I have been, to remove cowbird eggs or chicks.  In addition to being illegal, Audubon offers a rational argument for letting nature take its course.

Now for extra credit, see if you can identify the insects.  I edited a version of her video at this link showing just the food deliveries.  The challenge is to identify all twelve in order.  When you are through, compare it to the answer list below, but NO Cheating!

     1.   Moth
    2.    Hackberry Emperor butterfly
    3.    Dragonfly larva
    4.    Grasshopper
    5.    Dragonfly larva
    6.    Green Dragonfly larva
    7.    Damselfly
    8.    Dragonfly larva
    9.    Orange Sulphur butterfly
    10.  Dragonfly larva
    11.  Caterpillar, small, maybe a sawfly larva
    12.  Green caterpillar

 Other opinions will be cheerfully considered.