Archive for the 'Nesting & Courtship' Category

May 29 2014

Whooo Is That?

Three eastern screech-owl chicks perch on a branch, curious about the world.  They’ve just emerged from their nest hole and flown for the first time.  Everything is new.

“What is that over there?”  They bob and weave to get a better look.

Pat Gaines watched this owl family nest and fledge along the Spring Creek trail in Fort Collins, Colorado.  Click on the links below to see more of his photos:

These owls live in a part of the country were both eastern and western screech-owls occur.  Cornell’s Birds of North America says the two species are so similar that they can only be distinguished from each other by bill color and voice.

Neither species migrates so ornithologists have been able to pinpoint their ranges.  In Colorado eastern screech-owls live east of the Rockies, western screech-owls live west.  Their ranges have a narrow contact zone in Colorado Springs but don’t overlap.

It’s a place where birders ask the screech-owls, “Whooo are you?”

(video by Pat Gaines)

One response so far

May 26 2014

Proof Of Nesting

Ovenbird with nesting material, May 2014 (photo by Marcy Cunkelman)

The fact that it’s carrying dead grass tells us three things about this ovenbird:

  • It’s building a nest nearby,
  • It has a mate,
  • It’s female.

Back in 2004-2009 I participated in the second Pennsylvania Breeding Bird Atlas project in which we watched bird behavior and noted signs of breeding.   We learned that a bird is probably breeding if it’s holding territory, courting, or becoming agitated as we approach.  Its breeding is confirmed if the nest has eggs or young, or if we see an adult carrying food.  (Did you know that most birds don’t bother to carry food unless they’re feeding young? *)   The project was eye-opening because it forced us birders to slow down and observe what the birds are doing.

This ovenbird’s behavior — “Carrying Nest material (CN)” — is Confirmed or Probable nesting depending on the situation.  It’s true that an ovenbird carrying nesting material is a female and she already has a mate, but this is not true of all species.  In some, both sexes build the nest.  In others, such as the Carolina wren, the males build several “test” nests and the females choose.

Among ovenbirds only the female builds the nest and she doesn’t bother to do it unless she has a mate.  She chooses a depression of leaves on the ground and constructs a nest shaped like a beehive oven using grasses, plant fibers, weed stems, leaves, rootlets, mosses and bark.  When completed the nest is so well-hidden that it’s invisible from above.  Click here to see what the nest looks like with eggs inside.

Congratulations to Marcy Cunkelman on finding this ovenbird building a nest.  What a cool photograph.  I have never see this!

(photo by Marcy Cunkelman)

(* There are notable exceptions to the “carrying food” rule… worth learning.)

One response so far

May 16 2014

How To Build A Robin’s Nest

Mid-May is the height of robin nesting season in Pittsburgh.  The first nestlings have hatched and some are ready to fledge.

On Thursday I saw my first-of-2014 robin fledgling in Schenley Park.  Last month his mother spent 5-7 days building his nest.  This video shows her process in only 8.5 minutes.

While Mr. Robin sings in the background, his mate brings dry grass and drops it into place.  Her project looks sloppy for a while, then she does a cool thing.  She rapidly stamps her feet inside the nest while holding the edges with her wings and tail.  This makes the cup exactly fit her body.  How cool is that!

Halfway through Mr. Robin comes for a brief inspection.  Since he neither builds nor incubates, the nest is of passing interest to him.

When the cup is complete Mrs.Robin lines it with mud, then adds fine bits of dead grass to make the nest soft and lays her eggs.  (The last two steps are not in the video.)

Robins raise two or three broods per year and usually build a new nest for each brood.

What a lot of trips back and forth!

(video on YuoTube by richpin56)

5 responses so far

May 06 2014

On A Silk Foundation

Blue-gray gnatcatchers returned to Pennsylvania in April and set up shop immediately. As one of the earliest nesting insectivores they began courtship and site selection right away.

Nest-building is part of blue-gray courtship. Both the male and female build the nest and they make a lot of noise and exaggerated bows when they begin.  Meredith Lombard trained her camera on a nearby nest and filmed this pair’s efforts.

As you can see in the video, the nest is slightly expandable because it’s built on an elastic skeleton of spider webs and tentworm silk.  In the early stages of construction I’ve seen gnatcatchers chatter near decayed fall webworm tents, grab the silk and anchor it to their chosen site.  Later they poke the sides of the nest and stick in new bits of lichen and bark.  They also drag the silk upward to make the nest cup.

All of this activity makes them easy to find and watch.  Cowbirds watch them, too.  On Sunday I saw a pair of gnatcatchers harassing a female cowbird.  I hope they’re able to keep her away from their silky nest.

 

(video by Meredith Lombard)

One response so far

Apr 29 2014

Build And Sink

Franklin's gull (photo by Daniel Arndt)

As unusual as the gull that nests in trees, this one builds a floating nest.

Here in North America, Franklin’s gulls are prairie birds.  They spend the winter on the Pacific coast of South America, then migrate in Spring to the prairie marshes of Canada, Montana and the Dakotas where they look for shallow lakes to nest colonially.  Every year they assess the water depth and vegetation density when they arrive.  Droughts or floods force them to choose different marshes than they used the year before.

Like other marsh birds, Franklin’s gulls have learned that land-based nests are in danger of predation so they build floating nests out of bulrushes, cattails or phragmites.  To keep the nests from drifting they anchor them to underwater reeds.

Unfortunately the submerged material decays and the nest sinks so the pair and their oldest chicks add more nest material every day to raise the surface.

If you have to work this hard to keep your nest from disappearing you eventually find time-saving shortcuts.  Picking new bulrushes takes a long time, seven times longer than stealing your neighbor’s nesting material (someone actually timed this).  Naturally a lot of stealing occurs.

Build and sink, build and sink, the floating nest requires daily upkeep and annoys the neighbors.

 

(photo by Dan Arndt who writes for two blogs in Canada:  Bird Canada and Birds Calgary. Click on either blog link to see more of his work.  You’ll also see that they still have snow in Calgary right now. Yow!)

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Apr 12 2014

Holding His Own

Three healthy eaglets at Pittsburgh Hays bald eagle nest, 11 April 2014 (phot ofrom the Pittsburgh Hays eaglecam)

If you’ve been worried about the survival of Eaglet#3 at the Pittsburgh Hays bald eagle nest, you can ease your fears a bit.  Today the eaglets are 15, 13 and 10 days old.

On April 3 I described how competition among bald eagle siblings can cause the smallest eaglet to starve if food is scarce.   The good news is that the older they get, the better their chances for survival.

So far so good.  Eaglet #3 is active and growing and he’s getting fed.  Food is abundant. He’s holding his own.

The food supply is one more indication that Pittsburgh is a great place to raise a family.  But we knew that.  :)

 

(snapshot from the Pittsburgh Hays eaglecam.  Click on the image to watch the live stream)

Update:  Hmmmm. At 9:25am the three eaglets were very hungry and there was nothing to eat yet.  Eaglet#1 took a whack at Eaglet#3 who crouched with his face down to avoid attention.   Hmmmm. We shall see…

Eaglet#3 crouches to avoid another hit from Eaglet#1 (snapshot from the Pittsburgh Hays eaglecam)

17 responses so far

Apr 11 2014

Ruddy Bubbles

Ruddy ducks are migrating through Pennsylvania right now but we’re not going to see the most interesting part of their lives because they reserve it for their breeding grounds in the prairie potholes of North America.

Unlike most ducks, ruddies don’t court while they’re away from home nor do they molt into breeding plumage before they begin migration.  Instead they save their efforts for the big splash on the breeding grounds.  At that point the males will be a deep ruddy color and their bills will be sky blue.  They show off this beauty in an exaggerated bubble display.

Cornell’s Birds of North America describes the display like this (paraphrased):  “The male holds his head, tail and two rows of head feathers (“horns”) erect.  His inflates his neck and begins beating his bill slowly at first against his neck, forcing air out of the feathers.  This causes bubbles to appear in the water.  His beating intensifies toward the end of the display with a concomitant movement of his tail over his back and his head slightly forward over the water.  And then he utters a low belching sound.”

Who knew that male ruddy ducks bubble and burp?  I’m going to have to go West to see it.

(video from YouTube)

http://slatermuseum.blogspot.com/2010/11/ruddy-ducks-are-odd-ducks.html

3 responses so far

Apr 03 2014

Three Eaglets … For Now

Third bald eagle egg hatches at the Hays nest (snapshot from the Pittsburgh Hays eaglecam)

Yesterday afternoon around 5:00pm the third and final egg hatched at the Pittsburgh Hays bald eagle nest.  This happened during rush hour so a lot of us missed it … or did you stay late at work to watch?

Click on the photo above to watch the eaglet emerge from his egg.

An hour later all the eaglets are visible as Mom feeds the oldest chick.

Her actions reminded me that we will soon see a characteristic of bald eagle family life that’s quite different from peregrines’ —  the tendency for the oldest eaglets to thrive and the youngest to die, sometimes killed by their siblings.

Bald eagle eggs hatch asynchronously so each new eaglet is two days smaller than the previous chick.  Bald eagle parents feed the chick that asks for food, and since the oldest is bigger and more active he’s fed more than his siblings.  Eagle chicks are aggressive toward their siblings and the parents don’t breakup the fights.  The third chick often starves.  Cornell’s Birds of North America Online describes it this way, referring to a study in Saskatchewan:

Hatching asynchrony and differential growth leads to differential mass in siblings, facilitating competition and fratricide. Sibling competition and mortality is greatest early in nestling period, when size differences are greatest. Third-hatched chicks in Saskatchewan nests received little food and usually starved.

This behavior is quite different from the peregrines’ lifestyle.  Peregrine falcon eggs hatch almost simultaneously so all the chicks are close in age and size.  The last chick may be smaller at first because he hatches two days later, but peregrine chicks are not aggressive and their parents make sure everyone eats at every feeding.   Mother peregrines “chup” to their babies to encourage them to stand up and be fed.  Click here see how effective (and cute) this is.

For now there are three eaglets at the Pittsburgh Hays eaglecam … but be prepared for the day when there might be only two.

 

(videos and snapshots from the Pittsburgh Hays eaglecam)

30 responses so far

Apr 01 2014

A Threat To Bald Eagle Nests

Aerial photo taken after a logging operation along the Rappahannock River cut an eagle nest tree. This forest block supported a bald eagle nest for ten years prior to the harvest. Photo by Bryan Watts. (linked from The Center for Conservation Biology)

 

The Internet is captivated by the Hays bald eagle family nesting on a wooded hillside in Pittsburgh.  Their nest is protected by the Pennsylvania Game Commission and worldwide media attention, but what happens to nests that aren’t so famous?  Here’s the story of an unexpected consequence of removing bald eagles from the federal endangered list.

For 40 years bald eagles were completely protected by the Endangered Species Act (ESA) and everyone understood not to harm them.  By 2007 the birds made such a great recovery that they were removed from the federal ESA listing. Fortunately they are still protected by a law of their own, the Bald and Golden Eagle Protection Act that protects eagles, their eggs and their nests.

The Center For Conservation Biology (CCB) in Williamsburg, Virginia monitors bald eagle nests in the Chesapeake Bay area where 75% of the nests are on private land.  Each spring they fly over the watershed twice: once to count occupied nests, later to count chicks.  Last month CCB reported what they’ve found after 6+ years without ESA protection:  a real increase in the number of eagle nest trees cut down.

Bald eagles use same the nest for many years so when CCB flies over the area in early March, they look for known as well as new nests.  Increasingly they find former nest trees are gone, cut down when an area is wiped out by a large logging operation like the one above.

Private landowners apparently don’t realize the Eagle Act protects the nest, so the well-publicized de-listing of the bald eagle has lead to an unintended consequence:  disregard for the eagles’ habitat and nest trees.  CCB points out that education of landowners is sorely needed.

Click on the photo above to read the full story at The Center For Conservation Biology.

 

(photo of a clearcut along the Rappahannock River in Virginia, linked from The Center For Conservation Biology blog.  Click on the image to read the article)

2 responses so far

Mar 31 2014

Four Celebrities

Pittsburgh's Hays Bald Eagle family, 30 March 2014, 2 parents, 2 chicks, 1 remaining egg (photo from the Hays eaglecam)

Yesterday was a big day for the Pittsburgh Hays bald eagle family.  Their second eaglet hatched just after dawn, and the whole family was featured on ABC World News with David Muir.

Above, both parents feed the chicks on Sunday afternoon.

Click here for the ABC news segment.

Their third and last egg is due to hatch April 1.

Watch them “live” on the eaglecam.

 

(photo from the Pittsburgh Hays eaglecam)

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