Tag: Birds

Father Birds: Killdeer

Posted on by David Bookstaber

Killdeer are common birds of the plover family (like the mourning doves I showed in a previous post). Their name supposedly comes from their loud and distinctive call, which bird guides say sounds like “kill-deer,” though I don’t hear that at all. There’s a video of one at the bottom of this post so you can hear and judge for yourself. As with mourning doves, both parents stay to incubate and protect the eggs, which take 3-4 weeks to hatch. Killdeer chicks are precocial, meaning that they can walk and feed themselves soon after hatching. The parents still tend to them and protect them from danger. They learn to fly when they are about 3 weeks old.

Following is a gallery of photos I took of killdeer I found nesting in my yard. I was alerted to their presence by the antics of the mating pair protecting their four eggs. First was a persistent and attention-grabbing tweet. Once my eye found one of the parents, the bird began its famous “broken-wing” act, which is used to lure predators away from their nests: the killdeer will pretend to have an injured wing, dragging it and beating it against the ground while making pitiful cries. The idea is that a predator will follow the seemingly easy prey as the killdeer leads it further and further away from the nest. When the predator is far enough, the killdeer fly away. This actually makes it easy to find the nest: Just go in the opposite direction of where the killdeer is drawing you. The closer you get the to its nest the closer the killdeer will come to you in an attempt to distract you.

So I did find and photograph their eggs, but I didn’t want to overly traumatize the birds so I returned with my 300mm lens to get these photos from a reasonable distance.

The eggs are sort of camouflaged, but leaving them in a clutch like that on open ground still doesn’t seem to me like a great strategy.

Killdeer doing its “broken wing” distraction dance and cry.

Father Birds: Doves

Posted on by David Bookstaber

Mourning doves are one of the most common and widespread birds in North America. They get their name from the distinctive (and incessant) cooing sound they make. Male mourning doves are also devoted and protective fathers. In honor of Father’s Day, here are some photos of both parents caring for a fledgling.

Once a pair of mourning doves mates, they usually stay together for life. They work together to build a nest, usually on a tree branch or a ledge. The nest is made of twigs, grasses, and leaves, and is often flimsy and loosely constructed. The female lays two eggs at a time, which are incubated by both parents for about two weeks. The father usually takes the day shift sitting on the eggs.

After the eggs hatch, both parents feed the chicks “crop milk,” which is a thick mix of protein and fat they secrete in their crops (a part of the esophagus where they store seeds) and regurgitate for their chicks to eat out of their mouth.

Mother mourning dove feeding fledgling

The chicks grow to near full size and fledge in just two weeks! In these photos the fledglings are almost as big as their parents and will leave the nest in a few days.

Hummingbirds

Posted on by David Bookstaber

The word for hummingbird in most other European languages is colibri. I can’t find an explanation for why English didn’t adopt that. I put out a feeder with a 1:4 solution of sugar : water, and once they find it hummingbirds come for a drink every 15 minutes for the entire day. Here are photos of one frequent visitor:

Sometimes they perch, and sometimes they maintain a hover while drinking. They get a little territorial about the feeder, even though it has four perches and flowers to drink from: when one hummingbird is at the feeder, often another will approach and provoke it and they’ll flit away rapidly spiraling around each other.

Hummingbird species encompass not only the smallest birds but also the smallest warm-blooded animals. During the day they maintain the highest metabolism of any vertebrate. This requires a nearly constant supply of sugar. (At night, when they can’t feed, they perch and enter a hibernation-like state of vastly reduced metabolism called torpor.)

In terms of flying skills, they can keep their head perfectly still in a hover, even as their wings are fluttering back and forth dozens of times a second. I have seen them hovering at the feeder in the heavy winds preceding a thunderstorm. In the morning and evening I can see hummingbirds hovering and swooping to eat tiny flying insects.

No other vertebrates can maintain a true hover in flight, and the size range for hummingbirds runs from 2g to 20g. This suggests that any smaller and an endoskeleton and/or homeothermic metabolism becomes too expensive for a hovering animal. Any heavier and it becomes too difficult for a biological system to process and supply the energy needed to hover.

Vultures

Posted on by David Bookstaber

My house in Berwyn, Pennsylvania, sat on a hill overlooking dense woods and a small stream. Deer in that part of the state roam suburbia in large herds and, because hunting is severely restricted, their only predators are cars. Every few months a deer would end up dead down by the stream. (Why there? A wildlife officer explained that injured deer tend to go downhill and towards water, and so that’s where they die.) I could tell because vultures would start to appear in the tall trees near my house – black vultures and even larger turkey vultures, which seem to get along quite well. Hard to miss because they are massive birds, and before long they would be perched in large numbers and for days would swoop down to feed on the deer carcass until nothing was left but bones and hair. Here are photos I captured of these impressive birds:

A group of vultures congregated on the ground around a carcass is called a “wake.” Which is a very good description: Vultures are silent, so they seem like respectful mourners … aside from the ones that are actively picking at the carcass. A group of vultures perched in trees is called a “committee” – also a fine description as they will stand together solemnly on a branch for long periods.

It’s hard to convey how large these birds are. Their wings span 5-6 feet, and when they land it looks like their legs are flexing under a substantial weight.