Category Archives: Nesting & Courtship

Starting A Family In November

Barn swallow (photo from Wikimedia Commons)

Barn swallows (Hirundo rustica) are found on every continent except Antarctica, breeding in the northern hemisphere and wintering in the southern hemisphere with one notable exception: a small population breeds in Argentina. 

This behavior was unknown until 1980 when scientists confirmed that northern-born barn swallows had decided to nest during South America’s spring.  They’ve even shortened their return migration, traveling only as far as the equator during South America’s winter.

Scientists speculate that the birds are breeding in Argentina because we changed the landscape to their liking.  99% of barn swallows prefer to nest on man-made structures including farm buildings, bridges and boathouses.  They found what they like near Buenos Aires.

Barn swallows and nest on man-made structure (photo from Wikimedia Commons)

Because these swallows have flipped their north-south patterns a Cornell University study reports that this could be the first step toward a new species, similar to terns and skuas that have distinct northern and southern species (example: great skua and south polar skua).  For now, though, the Argentinian barn swallows still recruit northern-born swallows to join them.

Fledgling barn swallows beg for a food delivery from their parent (photo from Wikimedia Commons)

While we’re cold up here in North America, some barn swallows are starting families in November.

Read more about the Argentinian barn swallows here at Cornell CALS.

(photos from Wikimedia Commons; click on the captions to see the originals)

Whooo’s Out There?

Great horned owl (photo by Alan Wolf via Flickr, CC license)

What’s that noise in the backyard tonight? Who’s out there?

In autumn in Pennsylvania, great horned owls (Bubo viginianus) call to establish territory and court their mates. Their family time is coming soon. She’ll lay eggs before any other raptor species, sometimes as early as December.

Listen for their 5-note syncopated call: “hu-hu-Hoo HOO HOO

Great horned owl (recording by Ted Floyd, xeno canto XC344952)

If you’re lucky you’ll hear them “sing” a duet.  (Turn up your speakers to hear both birds in this recording.  The male’s voice is the lower one.)

Great horned owl duet (recorded by Daniel Parker, xeno canto XC144359)

Anywhere you live in North America, if there are woods or fields nearby great horned owls are there year round.

Range map of great horned owl (map from IUCN via Wikimedia Commons, purple color means year-round)

Sometimes they make very odd noises.

Great horned owl wak-wak calls, Pasadena, CA (recorded by Lance A.M. Benner on xeno canto XC337290)

Whooo’s out there? 

‘Tis the season for great horned owls.

(photo by Alan Wolf via Flickr, Creative Commons license, audio from Xeno Canto, click on the captions to hear the originals.)

Peregrines Nesting in Australia

Peregrine nestcam at Charles Sturt University, Orange, NSW, Australia, Oct 2018

Not only is New South Wales, Australia 15 time zones ahead of Pittsburgh, but the seasons are six months ahead as well. Right now it’s spring in the town of Orange, Australia and peregrine falcons are nesting.

Location of Orange, NSW, Australia (screenshot from Google maps)

Back in 2008, Charles Sturt University set up a falconcam on the nesbox at their Orange campus. This year there are two cameras and great views of the active chicks. (Click here or on the map caption for a closer look at where this is.)

The mother peregrine, Diamond, laid three eggs 21-24 August 2018.  The two chicks hatched on 25-26 September and have kept Diamond and her mate Xavier very busy ever since. 

News of the falconcam was late to reach me so the chicks are now five weeks old and growing their brown feathers.   

Tune in soon to see the nestlings before they fly.   Click here for the CSU Falconcams. Read the latest news at the Falconcam Project page.

(screenshot of CSU Camera One from the CSU Falconcam Project. screenshot of Google map of Australia.  Click on the captions to see the originals)

Sinks And Traps

Sink hole in Wales (photo from Wikimedia Commons)
Sink hole in a limestone region of Wales (photo from Wikimedia Commons)

Today’s blog about sinks and traps is not about plumbing …

bathroom sink (photo from Wikimedia Commons)

Last week Michelle Kienholz noticed that the mockingbird family near her office was under predation pressure again. In June half the family was eaten by a red-tailed hawk. On Friday two flightless young were frightened to the ground.  Michelle put them in a thick bush and hoped for the best.  I thought to myself, “That place is a biological sink for mockingbirds.”

Like a sink hole, shown at top, a biological sink is where a species breeds but the habitat works against them so they always fail to produce enough young to replace themselves. The population sinks at that site.

A sink can be offset by a high quality habitat called a biological source where the population more than replaces itself.  If the sources equal the sinks the population remains stable.  If the sources outweigh the sinks the population grows.  This balancing act is called source-sink dynamics.

Sometimes a sink is so attractive to breeders that they’re drawn to it in large numbers even though they always fail.  These ecological traps cause localized population crashes.

A good example of an ecological trap is the effect that outdoor lights have on mayflies.

Mayflies lay their eggs on water, often at night.  To find water in the dark they look for the polarized light reflection of the moon on water. Unfortunately, our outdoor electric lights are like thousands of moons that reflect off artificial polarizing surfaces — asphalt, cars, windows, etc.  The mayflies mistake these false surfaces for huge bodies of water and land there to lay eggs.  The locations are both sinks and traps.  All the mayfly eggs are wasted.

Mayflies on a car at Catawba Island, Ohio (photo by Rona Proudfoot on Flickr, Creative Commons license)
Mayflies on a car at Catawba Island, Ohio (photo by Rona Proudfoot on Flickr, Creative Commons license)

The number of mayflies that fall for these traps can be astonishing.  In June 2015 in Wrightsville, PA on the Susquehanna River, there were so many mayflies on the Route 462 bridge that the surface became slippery with dead mayfly bodies.  They had to close the bridge.

I suspect that if they’d turned off the streetlights while the bridge was closed, the trap would have disappeared, the mayflies would have gone elsewhere, and there would have been less to clean up.

(credits: video from WGAL-TV via YouTube.  photo of car with mayflies by Rona Proudfoot on Flickr Creative Commons license. All other photos from Wikimedia Commons. Click on the images to see the originals)

Eagle Productivity Drops For a Good Reason

Juvenile bald eagle at Hays, H8, 23 June 2018 (photo by Dana Nesiti)
Juvenile bald eagle at Hays, H8, 23 June 2018 (photo by Dana Nesiti)

Bald eagles have made an amazing comeback since the days of DDT.  From less than 900 birds nationwide in the early 1960s to more than 20,000 in the U.S. in 2007, their population more than doubled in Pennsylvania in the last 10 years.

At some point the number of nesting bald eagles will reach Pennsylvania’s carrying capacity.  What happens then?  How do bald eagles respond to match available food and nest sites?   We can look to Virginia for the answer.

Since 1964 the Center for Conservation Biology in Williamsburg has monitored and mapped bald eagle nests in the James River watershed.  Every year they do a flyover of the entire area to count both nests and chicks. Their eagle population grew from none in 1976 to a record 289 nests in 2018.  Meanwhile the number of chicks per nest — called “productivity” — rose sharply in the early years of recovery and now is dropping.  CCB announced this trend in two articles:

To see how this works, I have made a slideshow of two graphs from the Center for Conservation Biology’s article.  The bar chart is the count of nesting pairs, 0 to 289.  The line chart, the arc, is the average number of chicks per nest, 0 to 1.6.

As you can see, the number of nesting pairs continues to increase while the number of chicks per nest moves down.

CCB reports that in 2018 the number of chicks reached 1.09 and adds, “The two opposing trends appear to continue the population’s path to stability.”

“Productivity decline” sounds bad but it’s actually good news.  Breeding eagles respond naturally to accommodate lots of adults in the habitat.

So what does this mean for Pennsylvania’s bald eagles?

If the James River experience applies here, we’ll still see an increasing number of bald eagle nests that will eventually average one eaglet per nest.  We know bald eagles can produce more if they need to.  The good news is, they don’t need to.


p.s. See how rapidly the James River nest count grew!   Click here for CCB’s maps of the James River bald eagle population, 1990-2017.

(photo of juvenile bald eagle H8 at the Hays nest site by Dana Nesiti. Slideshow of two graphs from the Center for Conservation Biology article Eagle Productivity Continues to Slide.)

Gannets Galore!

Northern gannet in flight, Cape St. Mary's, NL (photo from Wikimedia Commons)
Northern gannet in flight, Cape St. Mary’s, NL (photo from Wikimedia Commons)

A week ago, on a Partnership for International Birding trip to Newfoundland, we visited Cape St. Mary’s Ecological Reserve during a rare fog-free moment.  Our goal was to see nesting seabirds up close at Bird Rock, one of the most accessible sites in the world.

Bird Rock is one of many cliffs at Cape St. Mary’s but it’s unique because it’s separated from the mainland by a deep chasm only a few feet from the trail’s end.  The birds are safe from land-based predators yet we could see them easily.

The main attractions are 24,000 northern gannets (Morus bassanus) who spend their lives on the ocean but return to Cape St. Mary’s every spring to breed with the same mate at the same nest.  Almost as large as bald eagles, their wingspan is 5.75 feet but they don’t weigh as much.  I love them for their size, sleek beauty, and their ability to plunge-dive at 50 mph to catch fish in the sea.

From the Visitors Centre we walked the trail across the barrens to get to the viewing area.

The landscape on the trail out to Bird Rock, 11 July 2018 (photo by Kate St. John)
The landscape on the trail out to Bird Rock, 11 July 2018 (photo by Kate St. John)

Pretty soon we could see the nesting cliffs. The white areas are all gannets.

Seabird nesting cliffs as seen on our walk out to Bird Rock at Cape St. Mary's, Newfoundland, 11 July 2018 (photo by Kate St. John)
Seabird nesting cliffs as seen on our walk out to Bird Rock at Cape St. Mary’s, Newfoundland, 11 July 2018 (photo by Kate St. John)

Near the trail’s end, Bird Rock is in the foreground.

Bird Rock and the cliff behind it are coated with birds, Cape St. Mary's, NL, 11 July 2018 (photo by Kate St. John)
Bird Rock and the cliff behind it are coated with birds, Cape St. Mary’s, NL, 11 July 2018 (photo by Kate St. John)

Here’s what we saw when we got there.  This 2011 video below (not my own) captures the sights and sounds of the colony.  The only thing you’re missing is the fishy smell of guano. It was filmed when most of the birds were still courting, wagging their heads and touching bills.  When we visited last week they were further along. Some chicks had already hatched.


The gannets hunt far and wide for fish to feed their chicks.  Just around the corner from Cape St. Mary’s in Placentia Bay there are loads of fish near Saint Bride’s. This YouTube video from 2017 (not my own) shows what I love most about gannets. They dive straight down to the sea!

Gannets galore!



p.s. The white spouts aren’t whales. They’re the splash-back from the gannets’ precision dives.

(first photo from Wikimedia Commons; click on the image to see the original. videos from YouTube. All other photos by Kate St. John.)

Growing Greener

Hope perches near a plant growing in the nestbox at the Cathedral of Learning, 24 June 2018 (photo from the National Aviary snapshot camera at Univ of Pittsburgh)
Hope perches near a plant growing in the nestbox at the Cathedral of Learning, 24 June 2018 (photo from the National Aviary snapshot camera at Univ of Pittsburgh)

The peregrine falcon nestbox at the Cathedral of Learning is growing greener.

A plant sprouted near the front perch and grows a little every day.  The seed probably came from the crop of a bird the peregrine family ate for dinner.  We’ll have to do some weeding when the nestbox is cleaned next fall.

Click here for a current view of the plant.

A NOTE REGARDING THE STREAMING VIDEO CAMERA:  The National Aviary’s streaming video contract lasts six months and will expire some time this summer, perhaps soon.  The stream will resume in February 2019 when the nesting season gets underway again.  In the meantime, see snapshots of the nestbox at this link.

(photo from the National Aviary snapshot cam at Univ of Pittsburgh)

Scenes Of Cardinal Family Life

Northern cardinals (Cardinalis cardinalis) are common backyard birds that we often take for granted though their family life is interesting.

Bob Kroeger photographed cardinals nesting in his Cape Cod backyard in May and June.  The slideshow lets us pause and see what they’re doing.

The male is very bright red:  This is good news for the family. Studies have shown that males with bright red breasts and females with bright underwings show more parental care to their young.

He feeds his mate at the birdbath:  The male’s job is to feed his mate from nest building through brooding (and perhaps beyond).  This makes sense because male cardinals don’t have brood patches.  The females build the nest, incubate the eggs and brood the young.

She’s eating away from the nest:   It’s perfectly normal for the female to spend time away from the nest, even if there are eggs in it.  During incubation, which lasts 11-13 days, the female spends 30% of daylight hours away from the nest.

Two juveniles on a branch with their father:  This cardinal couple beat the odds. The majority of nests fail due to predation.

How to recognize juvenile cardinals:  The juveniles resemble their mother but their beaks are dark.  (Adults have orange-red beaks.)  The juveniles’ beaks will turn orange-red when they are 65-80 days old.

You can’t see the food in the father’s beak:  The parents feed insects to their young but they  carry the food far back in their large beaks.  Researchers probably find this frustrating when they have to identify what the young are eating.

How long will the young depend on their parents?  Juvenile cardinals are completely dependent on their parents for about 19 days.  Around that time, their mother starts to build her next nest. Dad may feed the youngsters occasionally until they are 25-56 days old.


(photos by Bob Kroeger of South Dennis, MA: photos on Facebook; his business website.)

Nests Over Water

Green heron, Florida, March 2018 (photo by Bob Kroeger)
Green heron, Florida, March 2018 (photo by Bob Kroeger)

Why does this bird have his crest raised?

Perhaps someone came too close to his nest.

Green herons (Butorides virescens) are shy waders in swampy thickets, preferring to fish in the shadows and nest alone.  Because of their secretive nature it’s always surprising to find a nest.

When green herons return to Pennsylvania in the spring they’re already paired up for nesting.  The male chooses the location, usually in a small tree over water, giving preference to last year’s site if it was successful.  He starts to build the nest but as soon as his lady gets the hint his job is to bring the sticks as she places them.  Then she lays 4-5 eggs.

Green heron nesting in Florida, March 2018 (photo by Bob Kroeger)
Green heron nesting in Florida, March 2018 (photo by Bob Kroeger)

With this dual building effort it’s amazing that the structure is sometimes so thin that you can see the eggs through it from below.

That is, if you can find the nest.  Green herons don’t want you to.  They fly away loudly if you come too close.  Typically they sound like this (Xeno Canto 147343 by Paul Marvin at Viera Wetlands, FL)

… but if they’re really annoyed they are much louder (Xeno Canto 145806 by Paul Marvin at Viera Wetlands, FL)

Right now most of Pennsylvania’s green herons have young in the nest and the parents are busy bringing food.  At 16-17 days old the chicks will climb out of the nest — or swim if they have to.  They’ll fly at 21-22 days old.

Stay alert for the sight and sound green herons.  You might find a nest over water.

Bob Kroeger found these herons in Florida.


(photos by Bob Kroeger of South Dennis, MA. Bob photographs birds for fun and shares them on Facebook. Here’s his business website.)

Tarentum Peregrines: The Week To Watch

June 15, 2018:

The Tarentum peregrine family is already fun to watch. Now the excitement is ramping up.

Back on June 5, Gerry Devinney captured this video of the adult peregrines escorting an osprey away from their nest.  On June 8 Mary Ann Thomas wrote about them here: Tarentum Peregrines Defend Their Nesting Success.

Last Tuesday evening, June 12, the first nestling ventured out of the nestbox to ledge walk and exercise his wings.

We don’t know the chicks’ exact ages but they’re somewhere between 32-36 days old today. Young peregrines fledge at 38-45 days old.  These birds will fly soon, maybe within a week!

Visit the Tarentum boat launch to watch the youngsters get ready to fly.  Click here for a map.

UPDATE, June 15, 6:10pm:  Rob Protz reports that there are three (3!) young peregrines out of the nestbox this evening.


(video by Gerry Devinney)