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BACKYARD SECRET: GRAY CATBIRDS SEEM TO RECOGNIZE BROWN-HEADED COWBIRD EGGS

       The brown-headed cowbird does not build its own nest or raise its young.  Instead, it lays its eggs in the nests of other birds and leaves the arduous job of raising its young up to them.

       The brown-headed cowbird lays its eggs in the nests of more than two hundred species of birds.  The list of birds parasitized by this nest parasite includes backyard favorites such as northern cardinals, brown thrashers, and northern mockingbirds.

       In many cases, although their eggs look very different from the eggs of the unsuspecting host birds, the hosts accept them as their own.  As such, they end up raising cowbird hatchlings along with their own young.

       Interestingly, gray catbirds are rarely parasitized by brown-head-headed cowbirds.  Biologists believe this is because, unlike far too many birds, catbirds seem to be able to distinguish color and size differences between their own eggs and those of the cowbird.  As such, when a nesting catbird discovers a brown-headed cowbird egg in its nest, it unceremoniously removes it.

CHECK FOR BIRD NESTS BEFORE TRIMMING SHRUBS

        During the spring and summer, one of the worst things you can do is begin trimming a shrub around your home before checking to see if it harbors a bird nest. 

       The reason of this is common backyard birds such as cardinals, brown thrashers and mockingbirds routinely nest in the thick shrubs growing around most homes.  If you do not take this simple precaution, you stand the very real chance of exposing eggs or hatchlings to the weather and predators. 

       A few days ago, I decided to trim a loropetalum that had grown so tall it shrouded a window. However, before I cut the first branch I peered into the loropetalum’s thick foliage.  There suspended between the plant’s tangled branches was a cardinal nest. 

       At first glance, the nest seemed to be little more than a tangled mass of twigs.  However, as I looked more closely I could see that the female cardinal that had built this nest had also used a number of other building materials such as leaves, grasses, and strips of bark to fashion her nest.

       The nest contained only one bluish white egg marked with brownish splotches.  A gaping hole in the fragile egg indicated that a bird probably destroyed the egg.  A number of birds will peck holes in the eggs of another bird.  It was clear this nest was abandoned.

       The fate of this nesting attempt was not surprising.  It has been estimated that predators destroy upwards of 75% of eggs and young found in open nests such as this.  In the case of the northern cardinal, studies have revealed only 15-37% of all their nests fledge young.

       With such a low success rate, one might wonder why cardinals are so abundant around our homes.  One reason might be cardinals nest as many as four or five times a year.

       Since the nest in my loropetalum as was obviously abandoned, and cardinals typically nest in a different location each time they renest, I went ahead and trimmed the shrub. 

       On the other hand, if I had found the nest contained undamaged eggs or hatchlings, I would have put off my trimming for another day.

       With nesting cardinals facing such overwhelming odds trying to raise a brood of young, the last thing I want to is increase their chances of failure.  I know you feel the same way.

CAN MOCKINGBIRDS TELL ONE PERSON FROM ANOTHER?

The results of research conducted by University of Florida biologist Doug Levy suggest that it appears northern mockingbirds can indeed differentiate between certain people.

       In a simple experiment that could have been conducted in any yard where mockingbirds are nesting, Levy instructed a research assistant to walk up and touch an active nest four consecutive days in a row.  The researcher discovered the nesting pair was slow to react to the individual on the first day.  However, they became agitated more quickly when this large potential predator approached their nest each day thereafter. 

       Then, on the fifth day, when a different person approached the nest, he noted the birds became alarmed just a slowly as they did when the first interloper touched the nest for the first time.

       He concluded the mockingbirds quite possibly recognized the differences between the first and second research assistants.  It also suggests that this ability helps this popular backyard bird survive close to people.

       Perhaps this helps explain why mockingbirds we routinely see in our yards on a regular basis allow us to approach them more closely than they do strangers.

 

CHIMNEY SWIFTS FLY AND EAT ALL DAY LONG

        Without question, the backyard bird that spends more time flying each day throughout the spring and summer than of our other feathered backyard residents is the chimney swift. 

       From dawn to dusk, the bird Roger Tory Peterson dubbed the flying cigar is on the wing.  Biologists estimate that a chimney swift is capable of flying 140 miles every twelve hours.  During the nesting season, when the birds are feeding young, adult chimney swifts typically forage within 0.3 miles of their nest.  Although their flights can take them upwards of as high as 7,300 feet above the earth, most of the time, these aerial forays are much closer to the ground.

       Interestingly, in cities and other areas illuminated at night, chimney swifts will even hunt for insects attracted to outdoor lighting.  This begs the question, “When do they rest?”

       Indeed, feeding a nest full of hungry nestlings is quite a chore.  It has been estimated that a pair of adults feed their voracious offspring the equivalent of 5000-6000 housefly-sized insects a day!

       The diet of the chimney consists mainly (95%) of flying insects and spiders.  On the average, a chimney swift can eat as much as 1/3 its weight daily.  Among the delicacies consumed by chimney swifts are wasps, bees, aphids, mosquitoes (as many as 17,500 per day), ants, flies, and termites (up to 280 per day) to name but a few.  It should be noted that chimney swifts are a significant predator of fire ants.  In addition, they also capture tiny spiders drifting along in the wind on thin webs. 

       You would think that these small aerial wonders would pause to rest from time to time on a branch or utility wire.  The truth of the matter they are incapable of perching upright.  For the reason, when they are roosting in your chimney they use their tiny claws to cling to the vertical surface of the chimney.

       I think you will agree the chimney swift is one of our most fascinating backyard residents.

HOUSE SPARROWS SWIPE FOOD FROM OTHER BIRDS

      Soon after the first house sparrows were released in Brooklyn, New York in 1850 folks realized this seemingly gentle bird was actually contributing to the demise of eastern bluebird populations across the country.  When house sparrows and bluebirds competed for the same nesting cavity invariably, the house sparrow won out. 

       Later house sparrows earned the reputation of stealing food from a number of native birds.  This behavior is  known as kleptoparasitism.

       If house sparrows frequent your seed feeders, it is only a matter of time before you will witness this bizarre behavior.  Backyard feeder watchers have reported  watching house sparrows plucking seeds from the bills of a number of species of birds including red-winged blackbirds, northern cardinals, and common grackles.

       Away from our feeders, American robins are often the victims of this odd behavior.  House sparrows are known to stand alongside American robins as they hunt a lawn for earthworms.  As soon as a robin lunges forward and pulls a wriggling worm from the soil, the house sparrows swoop in, grab the prize, and fly away.

       Others have actually seen house sparrows following robins carrying food to their nests. Once there they literally take food out of the mouths of the robins’ hungry nestlings.

       It is amazing what you can see when you just take the time to watch.

       If you have seen house sparrows or other birds practice kleptoparasitism, I would love for you to share your sighting with me.

THE HUMMINGBIRD-SPIDER CONNECTION

       To many, hummingbirds and spiders represent a classic example of beauty and the beast.  In spite of that, spiders play a key role in the life of the ruby-throated hummingbird.  The thing that bonds these two very different creatures together is the spider web.

       Spider webs are extremely strong, sticky, and flexible.  Remarkably, based on weight, the strength of the web’s high tinsel strands is equal to steel.  Spiders use their amazing webs to capture food.

       The ruby-throated hummingbird visits spider webs to steal small insects that are captured by the web’s sticky fibers.  In addition, they will also actually prey on small spiders. 

       When the female rubythroat is building her nest, she plucks bits of the web to construct her nest.  In fact, spider webs are one of key materials used in nest construction.  The fibers help anchor the nest to the limb on which it is built.  They also cement the other construction materials that form the nest.  In addition, the stretchy fibers allow the nest to expand.  This is extremely important as it helps prevent rapidly growing young hummers from falling out of the nest.

       Spider webs also pose a risk to hummingbirds.  Each year countless hummingbirds become ensnared when they become entangled in a spider web as they try to glean nesting material or food.  In addition, others accidentally fly into a spider web spread across a woodland path or bed of flowers.

       When this happens, the likelihood of a hummingbird escaping a spider web is slim.  In some cases, when a spider senses a bird is caught in its web it will crawl to the bird and rapidly wrap it up in webbing just as it would a beetle or butterfly.

       In other instances, the spider simply allows the bird to struggle until it dies.  When this occurs, spiders will often cut an entrapped bird loose from the web and let it fall to the ground.

       If an ensnared hummingbird is extremely lucky, somebody will notice the bird and attempt to set it free.  In the vast majority of the cases, if the bird is found soon enough, it can be saved. 

       Should you ever find a hummingbird struggling in a spider web, immediately remove it.  Take the bird to a cool, shady location and remove ALL of the fibers adhering to the bird’s body.  This process can take several minutes.  Whatever you do, do not squeeze the bird as you are working.  Simply hold it loosely in one hand and gently peel away the tacky threads using a pair of tweezers.

       Once you have finished, hold the bird in your hand, and allow it to drink hummingbird nectar offered in the plastic lid to a soft drink bottle.  Dip the bill into the liquid.  In most cases, the bird will immediately extend its tongue into the fluid and begin feeding.  Never leave the bill in the liquid for any length of time.

       Feeding the bird before it is released will enable the hapless bird to regain some of the energy it expended while struggling for its life.

       When the hummingbird seems to have regained its strength, place the bird on the palm of your hand.  When it is ready to fly, it will suddenly begin rapidly beating its wings and fly away.

       If the bird doesn’t immediately respond after you have removed all of the spider webs from its feathers, place it in a brown paper bag and loosely fold the top of the bag.  Place the bag in a cool place.  Then check on the bird from time to time.  Once the hummingbird begins fluttering inside the bag, you know it is ready to be released.

       Believe me it is truly rewarding to see a hummingbird you rescued from certain death fly away.

 

BACKYARD SECRET: In Georgia, purple martins rarely nest in anything but gourds or nest boxes.

      The purple martin is a cavity nester.  Historically it nested in such places as woodpecker holes, natural cavities in trees and even in the crevices of cliffs.  Purple martins nesting in the western United States still utilize these traditional nesting sites.  However, since sometime prior to 1900, such is not the case in the eastern United States.  Here our largest swallow appears to have completely abandoned naturally occurring nesting sites. 

       In all of my years working as a wildlife biologist, I never encountered purple martins nesting in a natural cavity or woodpecker hole.  However, years ago I found a pair of purple martins nesting in broken light fixture at a convenience store. 

       As I pumped gas into my vehicle, I watched a purple martin bringing food to its young housed beneath the plastic cover over a fluorescent light illuminating the fueling area. 

       If you have ever seen martins nesting in anything other than nest boxes or gourds, please let me know.