Archive for the 'Bird Behavior' Category

Sep 20 2013

What’s All the Shouting About?

On vacation in Maine I saw a lot of gulls flying, posturing, and calling.

What was all the shouting about?

This video, filmed at Appledore Island, explains it all.

I wish I’d known this two weeks ago.  ;)

(video from Cornell Lab of Ornithology, featured in their September 2013 eNewsletter)

 

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Sep 10 2013

Sappy Nests

RBNU_9697353680_70396a3c93_rsz_shawncollinsRed-breasted nuthatch (photo by Shawn Collins)

Red-breasted nuthatches are the first bird I hear every morning in Maine.  What are they up to?

Right now they’re spending a lot of time caching conifer seeds to last them through the winter.  All summer long they ate arboreal arthropods (insects in trees) but now they’re switching to seeds, hiding them under bark or in sapsucker holes, covering the opening with lichen or plant matter. If there aren’t enough cones they move south, as so many did last winter.

Though they depend on cone-bearing trees for food, red-breasted nuthatches prefer to nest in dead or dying birches or aspens whose trunk is softened by disease or rot.  They often pick a birch with a broken top.  The lady digs the nest hole while her mate watches and brings her food.  She throws sawdust out of the hole leaving a telltale pile below the nest.  I’ve never seen this because I’m never in Maine during nesting season.

If I came here in the spring — or spent time watching the few red-breasted nuthatches who nest near Pittsburgh — I would see this amazing nesting habit:  To protect their eggs and nestlings they collect pine sap on the tips of their bills or on a little piece of bark, then smear it around the opening of the nest.  The male smears sap on the outside, the female smears it on the inside.  Experiments have shown this sticky mess keeps away both predators and competitors.

Adult nuthatches are very skillful at zooming straight into the nest without touching the sides — those who don’t are eliminated from the gene pool — so how do the nestlings fledge without getting stuck?  According to Birds of North America Online, parent nuthatches place small clumps of fur on the sticky inner nest rim on the day of fledging.

They make a stick-free launch zone for the kids to leave the sappy nest.

(photo by Shawn Collins)

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Jul 19 2013

Man, It’s Hot!

Dorothy panting to cool off after the banding (photo by Donna Memon)

Man, it’s hot here in Pittsburgh!  Yesterday the heat index was near 100 degrees.

We stay inside air conditioned buildings to avoid the heat but birds can’t do that.  Instead they use both obvious and amazing techniques to stay cool.

Just as we do, birds avoid heat.  They…

  • Reduce activity by roosting during the hottest part of the day.
  • Stay in the shade:  At midday Pitt’s peregrines roost on the north face of the Cathedral of Learning where it’s always shady.
  • Soar where the air is cool.  (Wish I could do that.)

Birds actively lose heat.  Dorothy used four of these techniques when she was overheated on Banding Day 2012 (pictured above).  Birds…

  • Pant.
  • Hold their wings slightly open.
  • Sleek their feathers to squeeze heat out of their downy undercoat.  That’s why Dorothy looks so thin here.
  • Expose the skin on their legs, wattles, etc. to lose water through their skin. Dorothy moved the feathers away from her legs so we can see her bands.
  • Gular fluttering:  Seabirds and nightjars can vibrate the muscles and bones in their throats to increase heat loss.  You’ve probably seen gulls doing this.
  • Bathe: We go for a swim, birds take a bath.  Vultures and storks don’t even have to find water.  They defecate on their legs to cool them off.
  • Turn on fans:  I’m not kidding. Scientists trained pigeons in 1975 to turn on fans when they were hot and thirsty.

And finally, some birds actually raise their body temperature.  This is amazing!  If your body temperature is warmer than the air you lose heat.  Hyperthermia can lead to heat exhaustion or death but some desert birds can raise their body temperatures in a controlled fashion to keep themselves cool.  Ostriches raise their body temperatures 4.2o C (7.5o F) every day. This saves water because they don’t lose any to cool off.

The weather forecast says today is the last of the unbearable heat before thunderstorms usher in a cold front.  I sure hope so!

In the meantime don’t be surprised to see birds with their mouths open.  They pant even when they fly.

 

(photo by Donna Memon.  Today’s Tenth Page is inspired by page 160 of Ornithology by Frank B. Gill.)

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Jul 18 2013

Dives Vertically to Capture Prey

Shikra, adult male (photo from Wikipedia)

What does this bird …

… have in common with this roller coaster?

SheiKra roller coaster, Tampa Bay, FL (photo from Wikimedia Commons)

The roller coaster was named for him.

The SheiKra roller coaster in Busch Gardens Tampa amusement park dives 200 feet at 70 miles an hour.  In the photo above, the sloped run takes the cars up.  The dive section is so vertical you could mistake it for a support strut.  Yow!

The coaster was named for the shikra (Accipiter badius), a hawk of Asia and Africa, because the hawk will dive vertically to capture prey.

He looks a lot like a Coopers hawk because both are accipters.  In fact he’s very similar in lifestyle and size to our sharp-shinned hawk.  When they’re upset they nearly sound the same.  Here’s the voice of a shikra, and here’s the voice of a sharpie.

I would not know of the shikra’s existence except for a Wikipedia article that featured the roller coaster.  When it mentioned a bird I had to look.

I love these connections.

(both photos from Wikimedia Commons.  Click on an image to see its original)

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Jul 16 2013

Arctic Summer Bird Activities

Red phalarope, Barrow, Alaska (photo from Wikimedia Commons)

Though the solstice was more than three weeks ago the sun still hasn’t set in the Arctic.  Some arctic animals have no circadian rhythm because there’s no light/dark cycle.  What do the birds do?

The Max Planck Institute of Ornithology studied four species that nest near Barrow, Alaska.  What they found is that some stayed on a 24-hour clock while others had no daily pattern.  Their circadian rhythms varied based on lifestyle, sex and breeding stage.  Here are the four they studied:

  • Semi-palmated sandpipers are totally monogamous and share incubation and child rearing.
  • Pectoral sandpiper males have multiple wives. Only the females incubate and take care of the kids.
  • Red phalaropes reverse these roles.  The females have multiple husbands.  Only males incubate and raise the kids.
  • Lapland longspurs are monogamous with the occasional male having multiple mates.  Both parents take care of the kids but only the female incubates.

During the courtship period the shorebirds showed no daily pattern while the lapland longspurs simplified their lives by never giving up their 24-hour clock.

Incubation changed the shorebirds’ clocks.  In summertime the ground temperature in Barrow varies daily from near freezing (11:00pm to 7:00am) to 60 degrees F (noon to 6:00pm).  As soon as incubation began the incubating parents — pectoral sandpiper females and red phalarope males — began to follow a daily clock so they’d be on the nest when it’s cold.

The exception were the semi-palmated sandpipers.  Because they completely share parental duties they threw out the clock when incubation began and synched as couples.  “Who cares what time it is.  We have each other.”

Meanwhile the pectoral sandpiper males and red phalarope females never stopped courting so they never developed a daily rhythm.

In the end the study shows that arctic-nesting birds are very flexible.  They can be active regardless of time of day, then alter their circadian clocks when their needs change.

Those needs will change soon.  The sun will set for the first time on August 1 and the birds will prepare to leave.  For some shorebirds, migration has already begun.

For more information read a summary of the study in Science Now or the entire study at the Proceedings of the Royal Society.

 

(photo of a female red phalarope in Barrow, Alaska from Wikimedia Commons. Click on the image to see the original)

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Jul 12 2013

Divorce Among Chickadees

Black-capped chickadee (photo by Shawn Collins)

“Birds are classically among the most monogamous of all organisms,” writes Frank B. Gill in Ornithology.

Many birds mate for life.  Swans and geese, parrots and eagles, albatrosses and even pigeons choose a mate once and for all.  Among those species divorce is rare.  That’s why a Bewick’s swan couple caused a stir when they arrived on their wintering grounds in 2009, apparently divorced and remarried.  They were the only Bewick’s swans known to do it in 40 years.

Do other monogamous birds ever divorce?  Is it typical behavior that we hadn’t noticed?

In 2000, Scott M. Ramsay and his team published an eight year study of black-capped chickadee social life.  Using bird bands and DNA testing they discovered that young females who have low confidence in their mates initiate divorce after their first breeding season and remarry on a more permanent basis for their second year of motherhood.  The team even found out why.

When black-capped chickadees pair up the males sing to maintain their territories and the females listen to determine who’s strongest.  When a first-year female hears her mate fail she remains with him but mates with other males as well, producing a clutch of mixed paternity.  She and her husband incubate and raise the nestlings but before the next breeding season she files for divorce and marries someone of higher social rank.

The study found that the ladies who “messed around” were the ones most likely to divorce.

No surprise there.

 

Read Ramsay’s famous study here.

(photo by Shawn Collins.  Today’s Tenth Page is inspired by page 360 of Ornithology by Frank B. Gill.)

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Jul 03 2013

What Do Birds Think Of Fireworks?

Fourth of July fireworks (photo from Wikimedia Commons)

Every year around the Fourth of July people use our neighborhood park to try out illegal fireworks.  (In Pennsylvania everything except sparklers, “novelties,” and toycaps are illegal without a permit.)

Last Sunday we jumped out of our skins when someone exploded a minute’s worth of “M-80″ salutes across the street.  After our hearts stopped racing and our cat emerged from under the bed I wondered…

What do birds think of fireworks?

I can guess based on our own reactions, but here are some scientific studies.

In the Netherlands where fireworks are popular on New Years’ Eve, the University of Amsterdam uses weather radar to track birds’ reactions when civilians celebrate at midnight.  On the radar here you can see thousands of birds fleeing en masse for 45 minutes.   The birds most affected are ducks and geese overwintering at quiet wetlands.  I suspect they are doubly susceptible because they aren’t habituated to human noise and they flee the sound of gunfire because they are hunted.

On the U.S. Pacific Coast a few towns have changed their fireworks venues to protect nesting seabird colonies.  When fireworks are too close the adults flee the cliffs exposing their young to cold or predation, or the young jump off the cliffs before they can fly.

At Depoe Bay, Oregon the fireworks display used to be held a mile north of town in a state park on a high cliff overlooking the ocean.  The site is part of Oregon Islands National Wildlife Refuge and has a large nesting colony of Brandt’s cormorants.  After July 4, 2011 and years of fireworks-induced nest failure the U.S. Fish and Wildlife Service began talking with municipal leaders about moving the venue.  USFW did a study showing significant nest failure and provided an alternate seaside location only a seven minute drive from town.  Most towns understand and accommodate.  Depoe Bay became famous for canceling and complaining.

So what do birds do about fireworks?   It depends.  Some flee.  Some hunker down.  Others are tolerant if the noise isn’t too close.  In any case the disturbance is temporary.

It’s pretty much our pets’ reaction too.

 

(photo from Wikimedia Commons.  Click on the image to see the original)

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Jun 25 2013

They’re Off the Clock

Published by under Bird Behavior,Mammals

Svalbard reindeer (photo from Wikimedia Commons)

Last Friday the solstice set our annual biological clocks.  Every day the sun triggers our circadian rhythm. But what if we lived where the sun never sets?  How would we synchronize our daily internal clocks?

In the arctic where day and night last for months a circadian rhythm would be annoying if not a handicap.  Since “day” has no meaning, arctic reindeer solved the problem by turning off their internal 24-hour clocks.

In mammals the circadian rhythm causes melatonin levels to rise at night and fall during the day.  This happens whether or not the sun gives us a cue.

Scientists studying reindeer in Norway (Rangifer tarandus, the same species as caribou) found that they have no rhythmic melatonin cycle.  Instead their melatonin rises or falls abruptly in response to light.  On or off.  No daily clock.

Reindeer need to know the time of year so they can synchronize migration and breeding, but this is easy to do at the equinox when the sun rises and sets.

On Svalbard where this reindeer lives, the sun rose on April 16 and won’t set until August 27.

No wonder he doesn’t care what time it is.  Some days I wish I didn’t care either.

Read more about this study in Science Daily, March 2010.

 

(photo of a Svalbard reindeer, a subspecies of Rangifer tarandus, from Wikimedia Commons. Click on the image to see the original)

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Jun 21 2013

Light Cues

Peregrine falcon tail feather (photo from Shutterstock)

Though Pitt’s peregrines, Dorothy and E2, are courting again today’s solstice will change that.

All living things have endogenous biological clocks that can run without light cues but we get out of synch with each other and the seasons in the absence of our external timekeeper, the sun.   Today our clocks struck twelve and began to head down again.

For peregrines in northern mid-latitudes the summer solstice ends their breeding cycle (initiated by the winter solstice) and triggers molting and preparation for migration.

Molting is a chilly and energy intensive activity in which birds replace all their feathers.  Since feathers provide warmth it’s cold to lose them.  Growing thousands of new feathers requires protein, increased blood to the feather sites, and changes in the birds’ calcium distribution.  And while flight feathers are being replaced flying is somewhat less efficient, an important consideration for precision-flying peregrines.

It makes sense to schedule this activity for a time when food is abundant and temperatures are warm.  Dorothy and E2 molt their flight feathers in July and August.  Good timing!

Our peregrines don’t migrate but arctic peregrines face an additional challenge.  They begin their molt in the arctic but don’t have time to complete it before they must leave on migration. Their bodies have adapted by starting the molt in the arctic, pausing during migration, and resuming at their wintering grounds in South America.  Very ingenious!

So when the sun paused this morning our birds got in synch.

We did too, we just don’t realize it.

(photo of a peregrine falcon tail feather from Shutterstock. Today’s Tenth Page is inspired by page 262 of Ornithology by Frank B. Gill.)

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Jun 17 2013

Doppler Effect

American avocet in flight (photo by Ingrid Taylar on Wikimedia Commons)

We all recognize the Doppler effect when an ambulance siren rises in pitch as it speeds toward us, then drops as it recedes. (Click here for a car horn example.)

Here’s a bird that uses that sound effect.

American avocets have many techniques for protecting their nests from predators.  They pretend to incubate a fake nest, then walk a few steps and pretend again.  They distract the predator by walking toward him in a teetering tightrope walk with wings outspread.  And they mob aerial predators before they can reach the nests.

But the most amazing technique is reserved for ground predators.  When avocets swoop to chase them away they shout at them, modulating their pitch to resemble the Doppler effect.  This is done so convincingly that the predator thinks the bird is approaching much faster than it actually is.  Run away!

Tex Sordahl discovered this while studying American avocets and black-necked stilts in the 1970s and ’80s.  Both use the Doppler sound effect.  I’m sure he got a dose of it during his study.

 

(photo by Ingrid Taylar via Wikimedia Commons.  Click on the image to see the original.)

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