March
15, 2009 - The cowbirds were the next of the blackbirds to come back
to us in multiples
this spring. The smallest of the blackbirds, they
comfortably fit on most feeders.
While the practice of laying and abandoning eggs in other song
birds' nests is historically understanding (What's a nomadic bird to
do?), we can't help but wish for a natural readjustment now that
this behavior is unnecessary and a burden and danger to other
innocent (albeit "shortsighted" - with the pun) birds.
The male cowbird is a strangely colored bird- an unusual two-toned
combination of dull brown with glossy black. The brown hood on a
blackbird body seems very odd at first. This bird is the smallest
of the blackbird gang that travels and forages together in the
off-breeding season.
The female is a very pleasant shade of tan with enough highlight
streaking to make her very pretty. For most people and other
birds, the cuteness ends with color. The female practices obligate
brood parasitism.. These birds must lay their eggs in the nests of other
species. Most of the other mamas will instinctively hatch and feed
these unusual babies often to the detriment of their own (cowbird eggs
hatch earlier and the hatchlings tend to be larger and more aggressive).
The female of some species can immediately recognize these strange eggs
and quickly destroys them.
The cowbird female has completely lost the ability to construct nests
and incubate her own eggs. The name cowbird was given to them
as they would travel with buffalos and feed on their parasites.
Because they followed "where the buffalo roam", the cowbird never had
time to build nests, lay eggs and raise their young. Their
survival meant finding an alternative method of perpetuating the
species.
There are differing opinions on the impact of this behavior on the
other songbird populations. Some believe that there is no real proof
that any other bird is truly being threatened by this practice and there
are other factors responsible for less birds. Others credit the
diminished numbers of certain song birds directly to the cowbird
practice of placing their eggs in other nests and the larger babies dominating nest activity.
| Size:
|
Length: 7.5-8 in Weight:
1.5 oz
Wingspan: 12 in
|
|
ID:
|
Male: Glossy green-black body with chocolate
brown head; short conical gray bill; tail short and squared;
black feet anisodactylous (three toes point forward and one toe
points backward)
Female: Grayish brown upperparts; paler underparts with faint
streaking; light colored throat
Juvenile: Paler than females; upperparts have paler scaly
looking edging; throat grayish
white |
| Habitat: |
Woodland edges, fields and pastures with
cattle, residential areas, campgrounds, and roadsides |
| Diet: |
Insects, spiders, grain, seeds and fruits;
walks with tail cocked over back while foraging the ground
|
| Family
Behavior: |
Mating Habits: Promiscuous
Local Breeding Period: Mid-May
Nests: No nest; will lay eggs in other species nests
Eggs: May lay as many as 10-36 in a single season (usually 1 egg
per active song bird nest; grayish white with evenly marked
brown spot; host bird incubates 10-13 days
Nestlings: Born altricial (helpless, naked, eyes closed) and
stay in nest 10 -11 days; hatches and matures faster than host's
nestlings thus outcompeting the natural fledglings |
|
Social Activities: |
Gregarious; joins
flocks of other blackbirds for foraging and roosting after
breeding |
| Range: |
Southern Canada to Mexico
|
|
Vocalization:
|
Song consists of low bubbly notes followed
by high pitched whistles; flight call is a high whistle followed
by two lower notes |
|
Sighted in our Backyard |
February to July
Odd visits: December 2009 |
|
Lifespan: |
Up to 16 years |
