Monthly Archives: April 2010

Anatomy: Brood Patch

Bird Anatomy
Brood patch on a female kestrel (photo by Jared B. Clarke, Birding Saskatchewan blog)

23 April 2010

Imagine trying to keep your children warm on a cold night by hugging them to the outside of your winter coat. They will still be cold unless you open your coat and hug them to your skin.

Birds incubate their eggs and brood their chicks by “opening their coats” to keep their children warm. 

Feathers are great insulation so during the nesting season birds must develop a bare patch of skin — a brood patch — to allow the eggs to come in direct contact with their bellies.  The brood patch also has extra blood vessels close to the skin to heat the eggs.   At the end of the nesting season the blood vessels recede and the feathers grow back to keep the adult warm.

In species where only the female incubates, the male doesn’t develop a brood patch.  In peregrines, Birds of the World explains that both male and female peregrine have brood patches: “Both sexes have paired lateral brood patches.  Less well developed in male.” Peregrine couples share incubation.

If you watch the streaming webcams you’ll see the adult peregrines rock up-and-down and side-to-side as they settle on the nest.  This rocking opens the feathers that have curled over the brood patch and puts their skin in contact with the eggs or chicks.

Shown here is a brood patch on a female American kestrel, North America’s smallest falcon.  The person holding the bird reveals the brood patch and the downy black feathers surrounding it by blowing upward on the bird’s belly.  

Imagine how cold a brooding falcon can get in an updraft!

(photo by Jared B. Clarke, author of Bird Banding in Saskatchewan from his May 6, 2009 blog, Eggs have been laid)

Happy Hatch Day!

Peregrines


The peregrine eggs at the University of Pittsburgh began hatching tonight. 

Here is Dorothy and E2’s first chick, just hatched at 11:20pm, in a nighttime snapshot illuminated by infrared light.

The chick has flapped and moved its wing as Dorothy bends over it (red arrow).  Its head is resting on the eggshell.  We could even hear it peeping on the webcam. 

See more pictures below.  Watch the webcam here.

Happy Hatch Day!

 <= Dorothy looks down at the chick still inside the egg shell.


April 22, 11:18am, Dorothy feeds her first chick of 2010. Notice the pip holes in two of the other eggs. The pip hole in one of them is facing away a little.


April 22, 11:57am. Two peregrine chicks have just hatched.  Dorothy allows them to dry.


April 22, 3:06pm. Dorothy feeds four hungry babies. Only one egg is left to hatch.

(photos from the National Aviary webcam at University of Pittsburgh)

Don’t You Even Think Of It!

Nesting & Courtship


For those who love bluebirds, the sight of a house sparrow eyeing a bluebird box is both maddening and frightening. 

House sparrows are cavity nesters, just like bluebirds, but they are far more aggressive.  They are so territorial that they’ll claim multiple boxes and exclude all others from nesting even though they can’t possibly use them all.  What’s worse is that male house sparrows will kill adult bluebirds inside the nest box and peck the chicks to death as part of this territorial behavior.  

Many are the sad stories of house sparrow attacks and dead baby bluebirds.  Beakless Bluebirds and Featherless Penguins by Sister Barbara Ann tells of the success she had in raising two beakless bluebirds who survived an attack thanks to her care.  Not everyone has the time or skill to do this.

As bluebird monitors will tell you, there is no real way to exclude house sparrows because they are nearly the same size as bluebirds.  The only effective method is to trap every house sparrow and remove it. It is illegal to trap native birds without a permit, but house sparrows are non-native and invasive.  They can be trapped and removed. 

There are many Internet resources that explain how to do this.  Try the Bluebird Society of Pennsylvania and Sialis.org for starters. 

Right now is bluebird nesting season.  It’s time to trap this house sparrow.

Hey you, House Sparrow!  Get away from that box!  Don’t you even think of it!

(photo by Bobby Greene)

Pawpaw in bloom

Phenology, Schenley Park, Trees
Pawpaw flower (photo by Marcy Cunkelman)

Here is a most unusual flower that hangs like a bell, sometimes in rows.

It has three deep maroon petals, three green sepals, and if you look inside three curled maroon petals surround the pistil.  The flowers are small when they first bloom, but grow to two inches long.

This is the flower of the Common Pawpaw tree (Asimina triloba), blooming right now in western Pennsylvania.

Though named “common,” pawpaw is an uncommon understory tree that grows in hardwood forests and bottomlands.  I found pawpaw trees blooming last weekend in Schenley Park and at Enlow Fork.

Some people prize pawpaw for its 4-inch long lumpy fruit that has the consistency of mangoes and the taste of bananas.  I ought to like it, but I’m not fond those two tropical fruits.  If you try it, don’t eat the seeds (see the link above).

I was able to identify the flower because Marcy Cunkelman sent me this photo a year ago.  When I saw the pawpaw blooming I remembered her picture but not the name of the tree, so I looked it up when I got home.  Thanks, Marcy!

(photo by Marcy Cunkelman)

En Garde!

Bird Behavior, Songbirds


When I was a kid, Saturday afternoon TV often showed swashbuckling movies starring Errol Flynn as Robin Hood or Captain Blood. 

“En garde!” he’d shout and draw his sword. 

That’s what these hairy woodpeckers are doing. 

“Mine!” they’re saying to each other.  “Go away!”

According to Birds of North America, hairy woodpeckers use their bills when establishing their nesting territories.  (I’ve paraphrased it here.)  “In close encounters, they use a bill-waving display that includes jerky body movements and waving their raised bills as if dueling.  The birds may stop for a minute or more, remaining motionless, each with its body pressed against the tree trunk and bill pointed forward and slightly raised as if crouched for attack or defense.”

Marcy Cunkelman found these two fighting in her yard this month.  I don’t know how the contest ended but I know the fight was worth it.  Marcy’s yard is a rich wonderland for birds.

(photo by Marcy Cunkelman)

Anatomy: Cloaca or Vent

Bird Anatomy

For several weeks we’ve learned about body parts that are the same on birds and humans.  Today’s lesson is very different.

The cloaca is a bird anatomy part most people never see.  It’s under the bird and usually covered by feathers.

Cloaca (pronounced klo-A-ca) is a Latin word that means “to cleanse” and is aptly used to name the bird’s single opening for its urinary, intestinal and reproductive tracts.  Here it is on a great egret, circled in pink.

This multi-purpose “vent” may seem odd but male mammals have a single opening for urine and semen.  Birds economize further.  Everything happens at one location for them.

When birds mate, they touch their cloacas for a few seconds.  This brief “cloacal kiss” is just enough time to transfer semen to the female.

If you don’t like the sound of “cloaca” you can use the word “vent,” a prettier, alternative name.

(photo of the underside of a great egret, including cloaca, by Chuck Tague)