Birds adopt many strategies for care of their young

One question that tends to pop up every June in my email or on Facebook concerns the presence of hummingbirds.  The status of hummingbirds at my own home since their arrival back in April has been somewhat sporadic. I think this has been noticed by some other people, too.

MommyHummer

Photo by Bryan Stevens                                                                  A female Ruby-throated Hummingbird visits a feeders. Female hummingbirds in our yards in June and July are probably nesting residents.

The hummingbirds were scarce in April and May. When June arrived, their numbers began to increase.

However, this pattern that I saw this year is usually just the opposite. The hummingbirds are usually abundant in early spring, taper off in June and July, and then increase again in August and September. Basically, I think their numbers just naturally fluctuate. Some years we have more of them than other years.

There are other possibilities to explain the absence of hummingbirds. It’s always possible that hummingbirds, adhering to the philosophy that “the grass is always greener” elsewhere have taken to exploring a neighbor’s yard and gardens.

Hummingbirds, like many of the songbirds that spend the summer season with us, keep busy this time of year with the task of raising offspring. That alone could explain a temporary lull in their numbers in our yards and gardens.

BabyTowhee

Photo by Bryan Stevens                                                A young Eastern Towhee, not long out of the nest, looks for sunflower seeds in the grass beneath a feeder.

Many species of birds attempt to nest two or even three times during the summer nesting season. So far this year, I’ve observed nesting activity by a wide variety of birds, including Northern cardinals, brown thrashers, Eastern towhees, Eastern bluebirds, tree swallows, song sparrows, white-breasted nuthatches, Carolina wrens and downy woodpeckers.

All birds, from tiny hummingbirds that are mere inches long to an ostrich that can stand more than nine feet tall, start out as eggs. Birds have developed a range of ways to protect and incubate eggs to ensure the continuance of the species.

For many birds, the strategy is to produce as many young as possible in a limited amount of time. The hooded warbler, which spends the winter months in Central America, will usually make multiple nesting attempts in a season. The female constructs a cup-shaped nest, which is a design common to many of our songbirds. She will lay three to five eggs in the nest. Incubation of the eggs is a duty usually performed solely by the female, but her mate helps by guarding the nest and surrounding territory. Both parents feed the young once they have hatched after about two weeks.

Not all birds share in the task of caring for helpless young. For instance, the male ruby-throated hummingbird shows not the slightest inclination to assist the female with the duties of rearing young. All ruby-throated hummingbirds are raised by single mothers. Male hummingbirds spend the summer sipping nectar, dueling with other male hummers and courting multiple females.

Hooded warbler pairs, as is the case with many songbirds, share the work of feeding and tending young. Many of these young birds spend very little time in the nest after hatching. Hooded warblers have typically left the nest within nine days of hatching, although parents continue to feed the young as they learn to fly and care for themselves.

BS-Phoebe-Baby

Photo by Bryan Stevens                                    An Eastern phoebe fledgling perches on a tree branch.

Some birds, such as Northern Cardinals, often delegate the duty to the male for caring for young that have fledged from the nest. As the male trains and continues to feed the maturing young, the female cardinal often begins the work of building a second nest, laying another clutch of eggs and incubating them. Time is scarce. By getting a jump-start on a second nest, the female cardinal, if successful, may produce eight to ten new cardinals in a single nesting season.

John-James-Audubon-Common-Cow-bird.-1.-Male.-2.-Female.-3.-Young

A painting of Brown-headed Cowbirds by John James Audubon.

Some birds, however, have bypassed the necessity of nesting altogether. If all hummingbirds are reared by females, then all young cowbirds are from foster homes, or nests. Female cowbirds slip their eggs into the nest of other unsuspecting songbirds. The hooded warbler is often a victim of this practice, which is known as “nest parasitism.” Some experts have conducted studies that indicate as many as 75 percent of hooded warblers in some areas are parents to cowbirds foisted on them.

BarnSwallows.jpg

Photo by Bryan Stevens                                Young barn swallows in their nest await a delivery of food by their parents.

It’s not wise to condemn cowbirds for a behavior that would strike us as immoral. The peculiar reproduction strategy for the cowbird came about as a natural necessity. Cowbirds once followed the massive herds of bison across the North American continent, feeding on the insects and seeds displaced by the hooves of these huge animals. Since the bison herds stayed on the move, the cowbirds didn’t have the luxury of staying put for a couple of months to raise young.

The decimation of the bison herds could have proven a disaster for the cowbirds. That wasn’t the case, however, since these adaptable birds simply switched from following bison herd to doing the same with the enormous numbers of domestic cattle that inherited the range of the buffalo, or bison.

These are just a select few ways that birds succeed year after year in the never-ending effort to ensure the survival of the species for another generation. Many obstacles stand in their way. Any time you see birds bringing their babies to a feeder in your yard or a shrub in your garden, recognize this moment as a singular triumph for the labor and dedication our fine feathered friends have invested in this outcome.

JP-RedEyedVireo-Fledgling

Photo Courtesy of Jean Potter                                                                                                                A young Red-eyed Vireo calls for food while concealed on the ground after leaving the nest. As is the case with most songbirds, parents continue to care for young even after they have left the nest.

Advertisements

2 thoughts on “Birds adopt many strategies for care of their young

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s