Archive for the 'Nesting & Courtship' Category

Jun 16 2014

The Importance of Tail Streamers

Barn swallows in flight (photo by Cris Hamilton)

Because the barn swallow is very widespread and nests almost exclusively on man-made structures, it’s been easy to study this bird for a very long time.  One interesting finding is that Hirundo rustica’s long tail streamers (outer edge tail feathers) are an excellent indicator of the birds’ health and a predictor of breeding success.

Birds with the longest and most symmetrical tail streamers are the healthiest and most desirable mates.  According to Cornell’s Birds of North America, “Tail length tends to correlate with reproductive success, annual survival, propensity to engage in extra-pair copulation, parental effort, ability to withstand parasites, immunocompetence, and other measures of fitness.”

In other words, if you’re a barn swallow with a long symmetrical tail you’re really healthy, you get to choose the best mate, and your nest will be very successful.  You’re also likely to be an older bird because tail length increases with age.

The down side is that long-tailed females are fickle.  They always get the best mates but even when they’re paired up they often “mess around” with un-mated long-tailed guys.  “Thus long-tailed male barn swallows are cuckolded more often than their less attractive neighbors,” says Frank B. Gill.

The longer the tail streamers, the better the bird.  I’ll be watching their tails now.

 

(photo by Cris Hamilton. Today’s Tenth Page is inspired by page 340 of Ornithology by Frank B. Gill.)

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Jun 03 2014

Not Your Typical Backyard Bird

A pair of prothonotary warblers, Conneaut Marsh (photo by Shawn Collins)

This pair of prothonotary warblers at a nest box may give you the impression you can attract them to your yard if you install the proper box.

Not!

Surprising for a warbler, prothonotaries choose old woodpecker holes or nest boxes for their nests but they are picky about habitat.  They only nest in forested bottomland, flooded river valleys or swamps.

The male returns from Central America before his lady and places nesting material inside his selected site.  Often it’s over water.  When his lady arrives he hopes she’ll agree that he’s chosen the right place.  If she likes it she adds twigs, leaves, moss and rootlets to finish the nest.

You can’t convince this bird to nest in your back yard … unless your yard is a wooded swamp.

 

p.s. Thanks to Shawn Collins for the photo that sparked this topic.

(prothonotary warblers at Conneaut Marsh, photo by Shawn Collins)

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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)

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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.)

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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)

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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)

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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)

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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

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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)

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