Category Archives: Bird Behavior

How High Can An Eagle Fly? Can A Raven Follow Him?

Bird Behavior, Birds of Prey, Crows & Ravens, Musings & News
A raven harasses V, the new male bald eagle at Hays, 18 Oct 2023 (photo by Jim McCollum)

24 October 2023

On 18 October while Jim McCollum was taking photos of the Hays bald eagles a raven showed up and began to harass the new male eagle, nicknamed “V.”

10/18 – The new fella went for a fly about and got jumped by a Raven. The Raven chased him all over the sky. This guy needs to work on his fighting skills.

— Jim McCollum -> 40 Acres a.k.a. Hays Woods Enthusiasts
A raven harasses V, the new male bald eagle at Hays, 18 Oct 2023 (photo by Jim McCollum)
A raven harasses V, the new male bald eagle at Hays, 18 Oct 2023 (photo by Jim McCollum)

Jim’s photos were shared to the 40 Acres a.k.a. Hays Woods Enthusiasts Facebook group where Dave Dutzik remembered a story about crows that piqued my interest.

A little tidbit I read recently. Crows will lite on eagles backs and peck at their necks. The eagles don’t fight back just soar higher and higher until for lack of oxygen the crow passes out and falls off the eagles back. I’m not sure about the validity but it’s a good story!

— Comment by Dave Dutzik at 40 acres Facebook group

Is it a true story? Let’s look into it.

At what altitude does lack of oxygen affect birds?

Birds are the champions of high altitude and can breed and exercise (fly) at altitudes that kill humans. Some species are so well adapted to high altitude that they fly as high as a jet, over the Himalayas where humans die without supplemental oxygen. Even our North American songbirds fly high …

Migrating birds in the Caribbean(*) are mostly observed around 10,000 feet, although some are found half and some twice that high. Generally long-distance migrants seem to start out at about 5,000 feet and then progressively climb to around 20,000 feet.

— Stanford Birds: How fast and high can birds fly

(*) Migrating birds in the Caribbean = warblers!

Is lack of oxygen the reason why the crow leaves the eagle? No. The crow leaves because the eagle is no longer a threat or because the crow is tired.

How high can a crow, a raven and a bald eagle fly?

So the better question is: How high can a raven fly? Can a bald eagle follow him?

For more information see High-altitude champions: birds that live and migrate at altitude and this vintage article.

As High As A Jet

(photos by Jim McCollum)

Hundreds of Grackles in the Trees

Bird Behavior, Migration
Common grackle flock moving through the trees, Patuxent Research Refuge, Nov 2021 (photo from Wikimedia Commons)

18 October 2023

This month a flock of 100 to 200 common grackles has been hanging out at Frick Park, chattering in the trees and swirling in a dense flock whenever they’re disturbed. This is typical fall behavior for grackles and blackbirds but I wondered why they picked the park.

According to Birds of the World, common grackles (Quiscalus quiscula) are not very territorial during the breeding season and drop all rivalry in fall and winter. On migration and at overwintering sites they prefer to roost and feed in huge flocks, sometimes mixed with other blackbirds and some robins.

Common grackles roost near plentiful food but they don’t require wild places. Urban roosts are often favored on tree-lined streets or in parks. Their fall roosts in New Jersey can contain 3,000-500,000 birds (of which grackles comprise 33%).

This flock at Patuxent in Maryland looks to be 100% grackles.

Common grackle flock on the ground at Patuxent Research Refuge, Nov 2021 (photo from Wikimedia Commons)
Common grackle flock starting to swirl up at Patuxent Research Refuge, Nov 2021 (photo from Wikimedia Commons)
Common grackle flock mostly flown away at Patuxent Research Refuge, Nov 2021 (photo from Wikimedia Commons)

Get To Know Nature in New Jersey shows what it’s like to be in the forest with hundreds of grackles.

video by Get To Know Nature on YouTube

The huge grackle flocks probably won’t stay in southwestern PA for the winter. By December they are further south, as shown on the eBird Dec-Feb map below.

Common grackle sightings, Dec-Feb, past 10 years (retrieved from eBird on 3 Mar 2022)

But for now we have hundreds of grackles in the trees.

(credits are in the captions; click on the captions to see the originals)

They Hear the Sound of Distant Waves

Bird Behavior, Water and Shore
Wandering albatross at the Tasman Sea (photo from Wikimedia Commons)

17 October 2023

Like elephants, albatrosses can hear low frequency sounds below our range of hearing, a skill that’s very useful for their lifestyle.

Wandering albatrosses (Diomedea exulans) spend their lives making incredibly long journeys over the ocean. They are known to circumnavigate the Southern Ocean three times in one year, a distance of more than 75,000 miles (120,000 km).

Range map of wandering albatross (map from Wikimedia Commons)

To do this with the least amount of effort, they have the longest wingspan of any living bird — 8 to 12 feet (2.5 to 3.66m) — and use the wind to glide as much as possible.

The best gliding happens at updrafts over the water and the best updrafts are caused by large waves. So how do wandering albatrosses find those large waves? They hear them from very far away, possibly 1,000 miles.

According to Science Magazine, “Big waves produce a very low frequency sound, below 20 hertz, that can travel thousands of kilometers, particularly when they collide with long distance swells, such as when storms develop.”

Would an albatross approach or avoid these waves in the Southern Ocean?

video from Monthly Fails on YouTube

To figure out how the birds choose where to go, Samantha Patrick of University of Liverpool and her team tagged 89 albatrosses with GPS trackers at their breeding grounds on Crozet Island near Antarctica. When the birds returned a year later to breed again, researchers retrieved the tags and analyzed the data.

Geophysicists on the team combined the biologger recordings with infrasound monitoring data from Kerguelen Island in the Southern Ocean to build “soundscape” maps on the birds’ journeys. …

During their long-distance flights, the birds tended to change course whenever they encountered a loud infrasound, the team reports. The infrasounds often indicate wave turbulence, even storms—though it’s not yet clear how the birds make use of this information. The infrasound clearly impacted the birds’ behavior, although the scientists couldn’t identify a clear pattern of whether they avoided or aimed for these low frequencies.

— Science Magazine: ‘Voice of the sea’ may help albatrosses catch the perfect wind

We don’t know yet if they avoid or approach turbulent areas but we know they hear them. More study needed!

Turbulent sea (photo from Wikimedia Commons)

Read more in Science Magazine: ‘Voice of the sea’ may help albatrosses catch the perfect wind.

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

Peregrines Are Just Tiring Them Out

Bird Behavior, Peregrines, Water and Shore
Peregrine falcon looking for a meal (photo from Wikimedia Commons)

13 October 2023

When peregrine falcons migrate down the Pacific Coast in autumn they often pause at Canada’s Fraser River Delta to hunt shorebirds. Pacificnorthwestkate (@pnwkate) filmed one working a sandpiper flock at Roberts Bank.

Peregrines on the hunt hope to separate a single bird from the crowd because they cannot catch anything in such a tight flock. When a lone bird can’t keep up it becomes the peregrine’s dinner.

Flock of dunlin (photo from Wikimedia Commons)

Dunlin flocking behavior on the Pacific Coast changed after the peregrine population recovered in the 1990s. A study at the Fraser River Delta in 2009 found that dunlin quickly learned it was unsafe to roost at high tide during the day because peregrines were on patrol. Instead they began to spend high tide flocking over the open ocean, flying continuously for three to five hours.

A new study, published this month in Phys.org, looked at the interaction from the peregrines’ perspective and found that the falcons haze the dunlin flocks to keep them moving. Peregrine hunting success improved at the end of those 3-5 hours of continuous flying because the dunlin had to stop for a rest.

The hunting data showed that dunlins were at greatest risk of predation just before and just after high tide, and spent most of the riskiest period flocking. However, there was a sharp increase in kills two hours after high tide, because the dunlins were not flocking despite elevated risk. [They were resting.]

— phys.org: Peregrine falcons set off false alarms to make prey easier to catch, study finds

So the dunlin changed their behavior to avoid peregrine predation and the peregrines changed their behavior to wear out the dunlin. Peregrines have more stamina that dunlin.

Read more about the peregrines’ hunting strategy at Phys.org: Peregrine falcons set off false alarms to make prey easier to catch, study finds.

(credits and links are in the captions)

Birds Near Naples Are Flying More Than Usual

Bird Behavior, Musings & News
Rock pigeons in flight (photo from Wikimedia Commons)

12 October 2023

West of Naples, Italy there’s an area called Campi Flegrei (Phlegraean Fields) that contains the remains of a ruptured supervolcano. It has erupted many times over the past 315,000 years including an eruption 40,000 years ago that produced a huge ash cloud and may have driven the Neanderthals to extinction.

The region around the Gulf of Naples is very volcanic. There are vents at Solfatara in Pozzuoli where sulfurous steam emerges in an old crater. Pompeii and Vesuvius are across the Gulf.

Sulfur vents at Solfatara, Pozzuoli, Italy (photo from Wikimedia Commons)

Nonetheless it’s a lovely place to live by the Mediterranean. Towns, including Pozzuoli, Agnano and Bacoli, dot the crater edges and the flats between them. The area’s population is 500,000.

Scene from Pozzuoli, Italy (photo from Wikimedia Commons)

This slideshow of maps shows the towns among the remnants of the supervolcano.

Relief map of Campi Flegrei (image from Wikimedia Commons)
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In June 2023 scientists determined that there is a potential for rupture before an eruption at Campi Flegrei caldera, Southern Italy. (uh oh!)

In September the magma under Campi Flegrei began shifting again and caused more than 1,100 earthquakes in a month, some as strong as 4.0 and 4.2 on the Richter scale. The Guardian reported on 3 October: “The Italian government is planning for a possible mass evacuation of tens of thousands of people who live around the Campi Flegrei supervolcano near Naples.”

Years ago I learned that birds can sense when an earthquake is coming and they take flight before it hits. I suspect that the birds at Campi Flegrei are flying more than usual lately.

Read more about birds and earthquakes in this vintage article from 2016.

Birds Take Flight Before Earthquake

(photos from Wikimedia Commons, click on the captions to see the originals. Map credits: colorful relief map from Wikimedia, Fig. 1 map: Unrest at Campi Flegrei since 1950 from Potential for rupture before eruption at Campi Flegrei caldera, Southern Italy published June 2023 at Nature.com, Google map of the area with terrain)

Leave The Leaves

Bird Behavior, Songbirds
Fallen leaves in Schenley Park, Nov 2016 (photo by Kate St. John)

6 October 2023

In October we see woolly bear caterpillars (Pyrrharctia isabella) out in the open crossing the trails. Woolly bears overwinter as caterpillars so this month they’re busy looking for the perfect place to spend the winter in leaf litter, under bark, or beneath a fallen log.

Woolly bear, Isabella Tiger Moth caterpillar, 3 Oct 2018 (photo by Kate St. John)

Leaf litter is key winter habitat for a lot of insects including springtails, millipedes, earthworms, butterflies and moths.

Millipede(*) Hays Woods, Sept 2023 (photo by Kate St. John)

It also shelters salamanders and newts …

Red eft among the leaf litter in West Virginia (photo from Wikimedia Commons)

… and provides an insect hunting ground for birds including eastern towhees, dark-eyed juncos, robins and mockingbirds.

Eastern towhee, male (photo from Wikimedia Commons)

If you’ve been thinking about “wilding” your yard — even just a little bit — now is a great time to start. Leave the leaves. You don’t have to leave it messy. Here’s advice on what to do.

Leaving the leaves and other plant debris doesn’t have to mean sacrificing your yard to the wilderness. The leaves don’t need to be left exactly where they fall. You can rake them into garden beds, around tree bases, or into other designated areas. Too many leaves can kill grass, but in soil they can suppress weeds, retain moisture, and boost nutrition. 

Avoid shredding leaves with a mower. Raking or blowing are alternatives that will keep leaves whole for the best cover and protect the insects and eggs already living there.

If you decide you need to clean up the leaves and debris in spring, make sure you wait until late in the season so as not to destroy all the life you’ve worked to protect. 

— Xerxes Society: Leave the Leaves: Winter Habitat Protection

Take a break this weekend. Don’t bag those leaves! Just push them aside for wildlife. 🙂

(photos by Kate St. John and from Wikimedia Commons)

(*) p.s. The millipede was easy to photograph because it was dead, probably the victim of a parasitic fungus that prompts the millipede to climb high on a twig before it dies. I wrote down the name of the fungus when I took the picture but cannot read my writing. Perhaps it’s Anthrophaga myriapodia.

Do Blackpolls Sleep in Flight Over the Atlantic?

Bird Anatomy, Bird Behavior, Migration
Blackpoll warbler in PA, Oct 2020 (photo from Wikimedia Commons)

5 October 2023

Some birds are champion fliers, staying airborne for days or months at a time. Scientists wondered if birds sleep in flight and proved that they do in a 2016 study of great frigatebirds, finding that the birds either “sleep with one half of their brains active, or with both hemispheres shut down at the same time.” Read more in this vintage article, Asleep in Flight.

Blackpoll warblers (Setophaga striata) are also champion fliers making a non-stop fall migration over the Atlantic Ocean of 1,900 miles in 72 to 88 hours. Traveling at 27 mph, they launch from the east coast between Nova Scotia and South Carolina and fly to their only stopover in Puerto Rico or Hispaniola (Haiti & Dominican Republic), then on to northern South America.

The blackpoll’s transoceanic path was proven in a 2015 study by Bill DeLuca and the Vermont Center for Ecostudies. VCE writes:

Bill DeLuca (Northeast Climate Science Center) and VCE solved this great modern-day avian mystery. Using light-level geolocators attached to Blackpoll Warblers in Vermont and Nova Scotia, DeLuca and colleagues documented the longest distance non-stop overwater flights ever recorded for a migratory songbird. During October, Blackpoll Warblers initiate a ~3-day non-stop transoceanic flight of ~2500 km from the north Atlantic Coast to Hispaniola and Puerto Rico. Radar data show migrating songbirds fly at 2,600 to 20,000 feet while making this journey. After a few weeks, they fly onto Columbia or Venezuela where they overwinter. Their spring migration route takes them over Cuba to Florida, where they journey up the eastern US seaboard to reach their breeding grounds in late May.

— Vermont Center for Ecostudies: Blackpoll Warbler

Notice in this eBird abundance map for the week of 2 Nov that blackpolls are:

  • bunched up on the East Coast from Massachusetts to North Carolina
  • at a stopover on Puerto Rico and
  • early migrants have already arrived in South America.
Blackpoll warbler weekly abundance map, week of 2 Nov 2007-2021 (map from eBird Status and Trends)

Watch them throughout the year in this eBird abundance animation.

Blackpoll warbler weekly abundance map (animation from eBird Status and Trends)

Of course I wondered if blackpoll warblers sleep in flight during their 3 day transoceanic trip, but we won’t find out any time soon. Blackpolls are way too small to wear the sleep monitoring gear used on the great frigatebird.

(photo from Wikimedia Commons, maps from eBird Weekly Abundance; click on the captions to see the originals)

ebird species migration weekly abundance trends

Young Red-Tail Hunts at the Hospital

Bird Behavior, Birds of Prey
Young red-tailed hawk outside Shadyside Hospital (photos by Mary Tuttle)
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28 September 2023

On Saturday 17 September, my friends Mary and Bea were walking to the Bloomfield Saturday Market when they couldn’t help but notice a red-tailed hawk (Buteo jamaicensis) hunting on the lawn at Shadyside Hospital. Mary stopped to take his picture.

Perched on the blue sign, I can tell the bird is immature because his tail isn’t rusty red. In early June he was still in the nest. Soon he learned to fly, then to hunt. Now, months later, he can feed himself but he’s not an expert. It takes time and luck to get a meal.

In autumn young red-tails disperse on their first migration and every place they stop is completely new to them. Those that grew up in urban environments are unbothered by traffic and people so they may gravitate to open areas near buildings in search of prey.

This hawk was so focused on hunting that he ignored Mary while she took his picture. Read more about the hawk’s single mindedness in this article from 2009.

Single-mindedness

p.s. This red-tail may have been attracted to the noise of house sparrows tweeting inside that bright green hedge. There are always lots of them in there, but they shut up as soon as I look so I rarely see one. As far as I know, I’m the only one — other than a hawk — that peers inside that hedge. 😉

(photos by Mary Tuttle)

Juvenile Cooper’s Hawks Learn to Hunt

Bird Behavior, Birds of Prey
Two juvenile Cooper’s hawks in Frick Park, 14 July 2022 (photo by Charity Kheshgi)

22 September 2023

Every year young Cooper’s hawks (Accipiter cooperii) fledge in June/July and learn to hunt in July/August. As soon as they’re self sufficient they disperse, and then they start to migrate.

Cooper’s hawks eat birds for a living so they migrate with their prey. Their peak migration continues now through mid October at the Allegheny Front Hawk Watch.

How did they get to this point? Let’s take a look back to August as some young Cooper’s hawks perfect their hunting techniques in New Jersey. It involves a lot of jumping.

video embedded from PTZtv on YouTube

(credits and links are in the captions)

Peregrines Together in September

Bird Behavior, Peregrines
Ecco watches while Carla preens, 15 Sep 2023, 3:54pm

16 September 2023

Yesterday Ecco and Carla spent lots of time hanging out together at the Pitt peregrine nest. The snapshot camera’s motion detector captured their activity.

Beginning at 3:50pm the pair spent 45 minutes together, bowing, preening, and watching. When Ecco left, Carla continued on the perch for another half hour, then stretched and departed at 5:00pm.

Two minutes later Ecco landed at the exact same spot on the perch. Because female peregrines are larger than males, the switch from Carla to Ecco made it look as if the bird shrank.

Ecco preened for more than an hour, then stretched and vaulted up to leave at 6:13pm. All told, the peregrines were present on camera for nearly 2.5 hours.

This slideshow shows 144 minutes of their interactions in only 1 minute and 15 seconds. If you miss the captions on the first pass, don’t worry, the slideshow repeats.

(photos from the National Aviary snapshot falconcam at Univ of Pittsburgh)