Cape May

Cape May
(RE BERG-ANDERSSON)
Showing posts with label parasitizing. Show all posts
Showing posts with label parasitizing. Show all posts

Sunday, September 2, 2018

Why I Don't Like Cowbirds

It is the Sunday of Labor Day weekend and I am far from laboring. There is a large spider on one of the poles holding netting in front of the hummingbird feeder, taking in some sun. The squirrels don't seem as active in the trees. As usual, people are not rushing around in their cars or with their lawn mowers. There is the faintest tinge of red in the leaves of the dogwood, another signal that summer is ending, the days are getting shorter and soon I'll be closing up the garden and taking in plants for winter.

Male cowbird, Cape May, NJ (RE Berg-Andersson)
Birds should've ended their breeding and raising of young by now. Many birds are on the move southward, taking advantage of those recent cooler days when the wind comes from the north to give them a push along.

However, amid this sluggishness I hear a high-pitched chatter I recognize. Then I see them, the male cardinal flying across the yard with a begging, scolding, badgering cowbird chick close behind.

It has been some time since I've seen this. Cowbirds are a peculiar species, at least to me. The only way the species can continue is the female - a drag brown, easily overlooked or confused with something else - drops one of her eggs into another bird's nest. The egg hatches, usually ahead of the bird's own eggs, and the chick is usually bigger too. To make sure it gets fed, it can push the other eggs out of the nest, monopolizing the parents. This is what the cowbird chick in my yard was doing with the adult cardinal pair.

And yet, somehow when the chick grows to maturity it knows it is not a cardinal, a robin, a Carolina wren. It flies off and joins with other cowbirds in large flocks, frequently joining with even larger flocks of grackles, redwinged blackbirds and starlings in winter as a way of finding food and protection.

When the adults pair, they are not monogamous and the female can lay eggs from a number of mates in the nests of more than 220 species of birds, according to the Cornell Lab of Ornithology. (Yellow warblers have been known to recognize cowbird eggs and build a new nest and lay a new clutch of eggs over the old. Other birds toss the cowbird eggs out. Cowbird eggs placed in goldfinch nests don't survive because goldfinches eat only seed rather than the insects a cowbird needs.)

Male cowbird flock, Cape May, NJ (RE Berg-Andersson)
Some people find the male cowbird handsome but I do not. These birds were once found solely on farms, following cattle (hence their name). However, according to the bird people at Cornell, once the open grasslands became towns and suburban developments, the birds spread. Now you are as likely to see them at your feeders. I try to chase them off mine whenever possible.

I pity the cardinal. This species seems particularly vulnerable to the parasitizing of its nests. It does not see a cowbird when the bird begs to be fed, it sees young and must feed it. The adult bird is programmed to do that. It does not "see" that this is not a cardinal. In fact, both parents are "blind" to that fact. All they know is the bird must be raised to fledge and then fed until it can take care of itself so it can mate and continue the species next year.

Luckily, cardinals, unlike several other types of birds whose numbers are down because of the cowbird as well as habitat destruction, are far from endangered. They will have several broods a year. There are many cardinals. They will come to my feeder and I will keep it filled for them. 

Unfortunately, cowbirds aren't endangered either. For now, I will have to put up with hearing the continual, annoying, badgering, high-pitched begging whine until something in the cowbird's mind tells it it's time to go find more of its own kind.


Saturday, June 6, 2015

Birds I Don't Like

Every year, after the winter birds have left for their summer homes, catbirds arrive to make nests in my shrubs. My trees are filled with little birds that have found old woodpecker roosts  or other natural crevices to make their nests. The box I put out for the house wren every year gets a tenant.

These are summer visitors I welcome. Others are not.

This year I've discovered common grackles nesting in my large, unshorn juniper hedge that acts as a screen between me and my neighbor. Deer have decimated the bottom of this hedge, which is why I leave the top part alone. Black-capped chickadees and other birds roost there for the winter and I know cardinals nest there during the New Jersey breeding season.

Delmarva female Boat-tailed Grackle (RE Berg-Andersson)
So to have grackles does not please me. They are large birds that, when not paired for breeding, congregate in huge flocks that are frequently augmented by blackbirds, cowbirds and starlings. They descend like a black cloud on my lawn several times each fall and spring. If left out the house feeder would be completely covered. I have also seen grackles attempting to get at seed from my encaged feeders. 

There are people who like grackles. Their black feathers show blue and brown highlights in the sun because of the luminescence. Jack Kerouac's mother, Memere, loved feeding the "black birds" after Jack dragged her down to Florida during one of those times he wanted to get away from the notoriety of writing "On the Road."

It doesn't take much for a grackle pair in a tree to turn into a huge flock in that and surrounding trees, crowding out other nesters. Grackles are opportunists, and like starlings and house sparrows - other birds I do not like for a variety of reasons - they will eat garbage left on the street as well as the worms they can pull out of the ground.

So I am not happy to see the three grackles (a pair and a helper?) walking along my lawn or pulling insects out of the crevices of my trees. 

These grackles, as I said, are common grackles. Along the eastern coast there are boat-tailed grackles, which are bigger and whose tails look like hulls. Unlike the common grackle female, which is the same color as the male but smaller, the boat-tail female is brown, such as the one above. That is usually how I know what kind I am seeing. The third type of grackle is the great-tailed grackle, a bird of the southwestern U.S.

It might seem strange that someone who enjoys walking around and looking at birds would have an antipathy to some species. My husband says all birds are God's creatures and have to feed where they can (although he does run out to grab the house and suet feeders when grackle "invasions" take place). 

I see no contradiction. After all, there are people I dislike but I don't hate the species.

The only bird I dislike more than the grackle is the cowbird. There are three types -- the brown-headed that I see in New Jersey; the bronzed I've seen once, in North Carolina; and the shiny cowbird. My comments pertain to the brown-headed.

Male Brown-headed Cowbirds, Cape May, NJ 2015 (RE Berg-Andersson)
I've written of my dislike of this parasitic bird before (please see my post of June 12, 2011; unfortunately, the link doesn't work). Besides hogging feeders, the female lays her eggs in the nests of other birds, usually one per nest. The cowbird chick usually hatches earlier and is much larger. It usually throws the other eggs out of the nest and dominates the attention of the parents. Then, somehow, it leaves the nest and knows to join up with other cowbirds, starting the cycle anew.

There is nothing sadder than seeing a cardinal being chased around the yard by a screaming, hungry cowbird chick. I usually see this every year. Actually, there is something sadder -- the Carolina wren pair I saw in another backyard one year, feverishly trying to feed the screaming "baby" chasing them that was twice their size.

Like the grackle, starling and blackbirds, the birds don't "sing" so much as croak out strange noises. The male cowbird is black with a brown head, the female a dull brown. They frequently pick at things in large flocks on roadsides, either with other cowbirds or alongside grackles and starlings.

About the only thing grackles and cowbirds are good for is diversifying the species. But these birds are tough and crowd out the smaller and weaker. Like other bullies, they are in no danger of disappearing anytime soon.

Prejudiced? Guilty.

Sunday, June 12, 2011

Love is Blind

I do not like cowbirds.

They are ugly birds. The male is black with a brown head that looks all black in dim light. The female looks like an oversized, gray house sparrow.

I do not like the female because she also has an ugly habit of dropping eggs in the nests of other birds. This is known as parasitizing.

The cowbird isn't the only bird to do this. Some cuckoos drop eggs into the nests of other cuckoos, for instance.

But parasitizing is the only way the cowbird can continue the species. Cowbirds don't build nests. Nor do they kick out other birds to take the nests, as owls do. It is not known why they must use the nests of songbirds.

That is why at this time of year, when I am hearing the first broods of chipping sparrows, starlings, robins and titmice making a ruckus as they chase their parents begging to be fed, I expect my annual sighting of some pair of adult birds being harried by a particularly large, aggressively hungry chick.

One year I was walking to the train and saw a pair of carolina wrens feverishly trying to fill the mouth of a cowbird chick that was double their size. Cardinal nests are also prone to parasitization and, like the sun rising in the east, I will soon hear the very loud screeching of the cowbird chick in my bushes following an adult cardinal that is desperately looking for something to feed it.

You would think the wren, for instance, would recognize the intruder in its midst. Some types of bird do. The yellow warbler will build an entirely new nest over an existing nest if it spies the larger cowbird egg, neglecting its own eggs in the process of starting over.

But most birds, like the carolina wren and the cardinal, are not programmed that way. If there is an egg, the adult sits on it. And if that slightly larger egg hatches first, as cowbird eggs do, and the chick manages to push some or all of the other eggs or hatchlings out of the nest in order to hog the food, it isn't noticed by the parents. In their minds, they are raising the next generation.

But it's the wrong generation.

In Michigan, where the population of Bachman's warbler was practically wiped out thanks to a nasty combination of habitat destruction and parasitization, it is policy to catch and kill cowbirds within the designated Bachman warbler jack-pine habitat.

It may seem cruel but that has helped the Bachman's population slowly re-grow.

This isn't a problem for the cowbird. This is one bird where the destruction of its usual habitat has helped it.

Cowbirds were farm birds, picking bugs off the cows and the fields. But with "progress" has come suburban developments built on farm fields. There may be fewer farms but the cowbirds adapted and thrived. Too well, in fact.

One thing that amazes me is that after being raised by a pair of cardinals, for example, the cowbird chick will grow up and somehow intuitively know it is not a cardinal. Then it will find other cowbirds and at the correct, programmed time mate and start the parasitation process all over again.

To me this makes the cowbird, literally and figuratively, the dark side of nature.