Category Archives: Migration

Monarchs On The Move

Monarch butterfly flying away in Iowa, Sept 2018 (photo from Wikimedia Commons)

In the past week I’ve noticed many monarch butterflies in flight and they’ve all been heading south.

When you see a monarch, pay attention to the direction it’s heading. Right now is the peak period for them to pass through Pittsburgh on their way to Mexico.

Monarch butterflies are on the move!

(photo from Wikimedia Commons; click on the caption to see the original)

Broad-winged Migration

Broad-winged hawk at Bent of the River, Connecticut, Sept 2016 (photo from Wikimedia Commons)

Every year, beginning in late August, broad-winged hawks (Buteo platypterus) head south on a 4,500 mile journey from their nesting territories in North America to their winter grounds in Central and South America.  It’s a journey many of us witness at Pennsylvania hawk watches. 

Unlike other hawks, broad-wings usually travel together. Though not in organized flocks they cue off each other to find the best travel conditions. This brings them together on migration.

The Allegheny Front Hawk Watch, 1.5 hours from Pittsburgh, saw 119 broad-winged hawks last Saturday but will peak September 13-15 with close to 2,000. Other Pennsylvania hawk watches will count even more.

Visit to see the latest statistics and find a hawk watch near you. Plan a visit soon.

Broad-winged hawk on migration, Bentsen Rio-Grande, March 2018 (photo by Bettina Arrigoni via Wikimedia Commons)

Meanwhile, keep looking up. There’s a good chance you’ll see a broad-winged hawk overhead in the next couple of weeks.

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

Unusual Visitor In Duquesne

Yellow-crowned night-heron in Duquesne, PA (photo by Oliver Lindheim)

In August 2019 a rare bird showed up every evening at an industrial park in Duquesne, PA. The bird was outside his normal range, but this is not surprising for a juvenile yellow-crowned night-heron.

Yellow-crowned night-heron in Duquesne, PA, 18 Aug 2019 (photo by Amy Henrici)

Related to egrets and bitterns, yellow-crowned night-herons (Nyctanassa violacea) live near water and eat mostly crustaceans. Some live year round in Central and South America. Others breed in North America and migrate south for the winter as shown on the map below.

Range map of yellow-crowned night-heron, yellow is breeding range (map from Wikimedia Commons)

However, juvenile yellow-crowned night-herons are great wanderers. As Cornell Lab’s All About Birds explains, “After the breeding season, young birds often disperse to the north or west before heading to wintering grounds.” That’s how they end up in Newfoundland, North Dakota and Duquesne, PA.

At 4pm on Sunday August 18, I went to see him at the industrial park but he wasn’t there because (duh!) he’s a night-heron. So I went back at 7:20pm.

He attracted a small crowd. Five of us watched him roam the sidewalks and grass beneath the pine trees at American Textile Company. He was so unafraid of humans that he walked right past two people standing on the sidewalk. This bird is completely focused on cicadas.

Yellow-crowned night-heron in Duquesne, PA, 18 Aug 2019 (photo by Amy Henrici)

To give you an idea how close he came, here are photos from Oliver Lindheim (at top) and Amy Henrici, two of the many birders who’ve made the trek to Duquesne.

Yellow-crowned night-heron in Duquesne, PA, 18 Aug 2019 (photo by Amy Henrici)

As soon as the glut of cicadas is over, this bird will be on his way.

UPDATE 26 August 2019: This bird is gone. He didn’t show up on the evening of August 21.

NOTE: If you went to see the yellow-crowned night-heron and you use eBird, please mark his location as the new “Stakeout” Hotspot created specially for him called “stakeout, yellow-crowned night-heron at City Center, Duquesne, PA.

(photos by Oliver Lindheim and Amy Henrici)

Captive-Raised Monarchs Fail To Migrate

Monarch butterfly on zinnia at Phipps Butterfly Forest, Aug 2017 (photo by Kate St. John)

In case you missed it, a monarch butterfly migration study published in the Proceedings of the National Academy of Sciences in June 2019 has troubling news for those who rear monarchs indoors.

Eastern monarch butterflies, famous for their autumn migration from North America to Mexico, have declined 80-90% in the last 20 years. To help the butterflies many people collect eggs and caterpillars in the wild and captive-raise them to increase their chances of survival. Unfortunately this well-meaning act can damage the insect’s ability to migrate.

Researcher Ayse Tenger-Trolander at Univ. of Chicago stumbled upon this when she purchased captive-bred butterflies for her monarch migration study. To measure their autumn migratory drive she placed them in a flight simulator and noted the dominant direction they wanted to fly. Wild migratory monarchs orient South. The captive-bred monarchs chose random directions, unlikely to migrate.

To further test the butterflies, Tenger-Trolander collected wild monarchs and raised a new generation indoors, mimicking outdoor autumn conditions. Here’s what she found.

Furthermore, rearing wild-caught monarchs in an indoor environment mimicking natural migration-inducing conditions failed to elicit southward flight orientation. In fact, merely eclosing(*) indoors after an otherwise complete lifecycle outdoors was enough to disrupt southern orientation.

Contemporary loss of migration in monarch butterflies, PNAS

Chip Taylor, Director of Monarch Watch, pointed out on NPR that some captive-bred monarchs do make it to Mexico, but added that “The real reason for raising monarch butterflies is for the enjoyment, the education. [T]he idea of individuals saving caterpillars as “monarch rescue” is misguided. “That’s simply not going to work as a way to boost the population,” says Taylor. “What we really need to do is to improve the habitat.”

We’re learning that monarch migration is complex and very fragile. It’s easy to break it in a single generation.

(photo by Kate St. John)

(*) “eclosing” means emerging from the chrysalis.

Red Admirals’ Mass Migration

Red admiral butterfly in April in Germany (photo from Wikimedia Commons)

Monarch butterflies are famous for migrating long distances from North America to Mexico but they’re not the only butterfly that travels far. Red admirals migrate, too.

Red admirals (Vanessa atalanta) occur in Europe, Asia and North America. Though the European population can hibernate, red admirals on this continent migrate south to places where their favorite host plant — stinging nettle — grows throughout the winter. In eastern North American they spend the winter in south Texas.

Over the winter a new generation of red admirals matures to fly north and repopulate the continent. We usually don’t notice them but in the spring of 2012 hot weather came so fast that red admirals passed through Presque Isle State Park in a couple of days on mass migration.

On Throw Back Thursday read about the amazing number of red admirals in 2012 in this vintage blog: Mass Migration.

Why don’t we see them migrating more often? Perhaps they’re traveling high above our heads. According to Wikipedia: “During migration, the red admiral flies at high altitudes where high-speed winds carry the butterfly, requiring less energy.” Oh my!

(photo from Wikimedia Commons; click on the caption to see the original)

Late April: What’s Next?

Great horned owl with yawning nestling, April 2019 (photo by Dana Nesiti)

Spring is popping in southwestern Pennsylvania. Here’s what to look for in late April.

  • Branching! Great horned owlets are growing up fast. At the earliest nests owlets will walk on nearby branches before the leaves come out. Dana Nesiti photographed this yawning owlet in early April.
  • Nest building: Songbirds are building nests especially American robins, song sparrows and Carolina wrens. House sparrows flutter by with cellophane for their nests.
  • Migration: Blackbirds and tree swallows are here. Gray catbirds are coming soon. Also Louisiana waterthrush, yellow-throated warbler, hermit thrush, ruby-crowned kinglet, blue-headed vireo, brown thrasher, blue-gray gnatcatcher, pine warbler, northern parula, chimney swift, barn swallow and house wren. See them on an outing with the Three Rivers Birding Club.
  • Trees: Flowering trees include redbud, downy serviceberry, cherry and more. “Leaf out” comes in early May.
  • Wildflowers: Violets, large-flowered trillium, trout lilies, Virginia bluebells and much more. Get outdoors with the Botanical Society of Western PA or Wissahickon Nature Club. Visit Enlow Fork on the last Sunday in April for the Enlow Fork Extravaganza starting at 8:00am.
  • Butterflies: Spring azures, cabbage whites, eastern commas, orange sulphurs, red admirals.
  • Turkey season: Be careful if you hear a turkey calling; it might be a hunter. Spring Gobbler hunting season runs from the last Saturday in April through all of May. Junior hunters get a one-day early start on the next-to-last Saturday (April 20).

In late April, spring is happening fast. Don’t miss it!

(photo by Dana Nesiti)

Why Birds Get Here Last

Map of 1st 2019 ruby-throated hummingbird sightings as of 11 April 2019 from Journey North

This time of year can be frustrating for Pittsburgh birders. Migration is underway and the “good birds” are everywhere but here. Why do we keep missing them? Is there something wrong with us?

It’s not us. It’s where we live. Sometimes the “good birds” get here last.

Ruby-throated hummingbirds are a case in point. Their arrival is tracked every year on the Journey North website (screenshot above) where we can see what we’re missing. In the very warm spring of 2012 they arrived in Ohio and Wisconsin by the end of March but weren’t in most of western Pennsylvania in early April. Hummingbirds surrounded us but they weren’t here yet.

On Throw Back Thursday, see the 2012 maps in this vintage article: Why Birds Get Here Last.

Watch the hummingbirds approach on Journey North’s 2019 first ruby-throated hummingbird map.

p.s. Our definition of a “good bird” is part of our problem. The “good” ones are uncommon so of course they get here last, if at all.

LATER THAT SAME DAY (Thursday April 11, 2019): As if to prove me wrong, birding was exceptionally good today with many new migrants that arrived overnight.

(screenshot of first 2019 ruby-throated hummingbird sightings as of 11 April 2019 from Journey North)

Where Are They Going?

Lesser black-backed gull (photo by Marek Szczepanek via Wikimedia Commons)

5 April 2019

In late March more than 440 lesser black-backed gulls congregated in a damp field in northeastern Pennsylvania — an exciting find because they used to be very rare in North America. Why are they here and where are they going? The Pennsylvania Game Commission is using satellite telemetry to find out.

Lesser black-backed gulls (Larus fuscus) are an Old World species that breeds in Iceland, northern Europe, Russia and Kazakhstan and spends the winter in Europe, Africa and coastal Asia. They were never seen in North America until one showed up in New Jersey in 1934. Slowly their wintertime numbers increased until they’re now considered non-regular winter visitors to North America’s Atlantic and Gulf Coasts. See the map below.

Range map of the lesser black-backed gull (image from Wikimedia Commons)

They still don’t breed in North America in numbers that count on that map. However, they might be thinking about it.

In 2007 a single lesser black-backed gull began breeding on Appledore Island Maine, paired with a female herring gull because there were no other lesser black-backed gulls around. (Lesser black-backed and herring gulls are closely related.)

Meanwhile their migration numbers through Pennsylvania are high enough that ornithologists began to wonder if lesser black-backed gulls are bothering to cross the Atlantic to breed. Are they going to Iceland? We would know that answer if we knew where the Pennsylvania flock was going.

Last spring the PA Game Commission attached satellite transmitters to nine adult gulls when they stopped over in Pennsylvania. The map of the gulls’ movements tells an interesting tale.

Screenshot of 9 lesser black-backed gulls’ movements in North America (map from PGC telemetry study)

The satellite-tagged gulls don’t go to Europe. They stay in North America. Based on their sedentary lifestyle in June they seem to be breeding in Greenland and northeastern Canada.

Screenshot of 9 lesser black-backed gulls’ movements in North America (map from PGC telemetry study)

Click here for the interactive Lesser Black-Backed Gull Telemetry map that zooms in and follows the gulls’ paths. (There’s more about the study here.)

Is there a breeding population of lesser black-backed gulls in North America now? This year we’ll watch again to find out where they’re going.

(photos from Wikimedia Commons, maps from PA Game Commission’s Lesser Black-backed Gull telemetry project; click on the captions to see the originals)

Tree Swallows Soon

Tree swallows fighting over a nest box (photo from Wikimedia Commons)

You might not see any tree swallows in Pittsburgh yet, but there are flocks in the north at Custards, Geneva Marsh and the Linesville Fish Hatchery.

Last Tuesday March 19 Patience Fisher and I were amazed by the millions of midges in the air at Custards. There were so many that they coated my car and attracted hundreds of tree swallows that wheeled over the marsh.

Tree swallows (Tachycineta bicolor) are short distance migrants who spend the winter as close to us as coastal North Carolina. The males tend to migrate first and arrive on the breeding grounds to claim territory and fight over nest sites, including bluebird boxes. When the females arrive they pair up quickly and place a little nesting material in their chosen nest site. The pair won’t nest for a few weeks but they like to stake their claim early.

Keep an eye out for tree swallows in the days and weeks ahead … and hope for warm weather so they have enough insects to eat.

Tree swallows are coming soon.

(photo from Wikimedia Commons; click on the caption to see the original)