Fall's Journey South Update: October 23, 1998
Today's Report Includes:
Predictable Surprises
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Photo: USFWS
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We all know that birds migrate every autumn in a predictable way, but every fall we learn new things about migration,
and every fall birds do unpredictable things. The most exciting part of being a scientist is learning things no
one ever knew before. People have been watching and studying birds for thousands of years, yet there is a lot still
waiting to be discovered. This week two scientists who correspond with Journey South made new discoveries. One
follows a Peregrine Falcon via satellite to learn more precisely how Peregrines migrate. The other is collecting
data from oil platforms on the Gulf. People on the platforms have been noticing birds for decades but it's only
been recently that ornithologists started collecting data there.
Follow a Falcon
Geoff Holroyd, a research scientist in Edmonton, Alberta, has been using satellite telemetry to follow
a female Peregrine Falcon that carries transmitter #5735. Geoff followed her signal all the way from Wood Buffalo
National Park in Alberta, Canada, as she moved southeast, which brings us to this week's
Challenge Question #8
- Read Geoff Holroyd's report below.
- Make a map of the course this falcon has traveled so far.
- Then answer Challenge Question #8: "How many miles has peregrine #5735 travelled?"
To respond to this question please follow the instructions
at the end of this report.
Peregrine with a Mind of Her Own
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Photo: Skip Ambrose
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Geoff Holroyd writes, "On July 6, I and Jeff Dixon, senior warden, Wood Buffalo National Park, caught the
female peregrine at her nest near Fort Chipewyan in northeastern Alberta. The falcon had 3 healthy young even though
she was only one year old. Often peregrines do not nest until they are at least 2 years old. We could tell her
age since one year old peregrines have a brown feathers on their back. By year two their back is slaty blue.
"By mid September, the female was making flights away from her nest site but returned daily. On September
17 she flew 63 km east to the south shore of Lake Athabasca.
Follow the movements of Peregrine #5735:
- Sept. 16--Fort Chipewyan, Alberta
- Sept. 17--63 km east; the south shore of Lake Athabasca
- Sept. 20--97 km west; Peace Athabasca Delta
- Sept. 23, 8 a.m.--Boisevain, Manitoba
- Sept. 23, 3 p.m.--Minnesota
- Sept. 26--Davenport, Illinois
- Sept. 29--Decatur, Alabama
- Oct. 2--Florida coast 50 km south of Tallahassee, Florida
- Oct. 5--Key Largo, Florida
- Oct. 8--Pine Islands, east of Key West.
- Oct. 11--north coast of Cuba. She was at the same location on October 14."
When she stayed there for three days and seemed to be settling it, Geoff figured she must be overwintering there.
She reminded him of the falcon they followed last
year that "traveled south very rapidly and stopped abruptly south of Veracruz, Mexico. It remained there
for the winter." As a scientist, it is Geoff's job to make predictions and test them. Geoff predicted that
this year's marked Peregrine would remain in northern Cuba.
But she didn't! On October 17, Peregrine Falcon #5735 had moved 535 km southeast, and was roosting in the foothills
of Sierra Maestra 30 km west of Santiago de Cuba. Then, "during the night of September 20/21, she roosted
on the south coast of Haiti, immediately south of Port-au-Prince. She is about 400 km southeast of her location
on September 17 on the south coast of Cuba."
Geoff wonders if she will continue southeast and fly over the Caribbean Sea to South America, or if she'll follow
the island chain east to the Leeward and Windward Islands. He promises to keep us up to date on where she goes
from there.
More Peregrine Adventures from the Gulf
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Location of the 5 oil platforms where scientists are based in Gulf of Mexico.
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Bob Russell, Journey South's correspondent from an oil platform on the Gulf of Mexico, had lots of news for us
this week, now that he's back on the platform after all that "tropical weather mayhem ended."
Bob told Journey North, "It's been literally a Peregrine cafe out here this fall. They have been common at
all platforms, and our farthest platform has had up to 18 Peregrines roosting on it at a given time. Their favorite
food seems to be Least Bitterns, Purple Gallinules, Green Herons, and Soras, though we rarely see these species
on the platforms." How do Peregrines find birds that the biologists don't? Bob explains, "The eyesight
of Peregrines must be phenomenal: sometimes a Peregrine will see a migrant over the water, and fly out so far that
I can barely see the Peregrine with 10X binoculars; then the falcon will fly back with its prey."
Many scientists assume that Peregrine Falcons do all their hunting in the daytime, but Bob mentioned, "Much
hunting is done at night during the active passage of migrants aloft. The presence of the platforms offshore has
clearly had a profound influence on migrating Peregrines."
Bob has been too busy with his data collection to have time to write about all the migration events he's seen this
fall, but he did put together a vivid account of a thrilling migration night on September
15.
Exciting Discovery in the Gulf
Bob told us that not only are the scientists seeing birds moving south, they also see, and find on radar,
birds moving north! "These northbound movements begin at first light, and they continue through morning and
even into the afternoon. Our platform-based work indicates that these return movements are composed primarily of
shorter-distance migrants that spend the winter along the Gulf Coast, and which accidentally "overshot"
the coastline during the previous night and are attempting to make it back to land." Bob notes that although
birds overshoot their destination on land as well as over the Gulf, they are easier to study from the oil platforms.
Why do you suppose that is?
Bob adds, "The commonest birds recently (well, before the latest period of extended SE winds) have been
Marsh Wrens and House Wrens," and he and his team have seen a host of other short-distance migrants. He says,
"Platform usage by these 'overshoot migrants' has been heavy, and because of the abundance of migratory moths
and other insects offshore during the fall, these birds are usually able to feed successfully. The existence of
a network of platform rest stops on which the overshoot migrants can stop and grab a moth snack is very clearly
beneficial to these birds!"
Migrating Monarchs and Other Insects Over the Gulf
Speaking of insects, Bob notes, "We finally started to see a few Monarch Butterflies--but only a few. Gulf
Fritillaries have been most common." They've seen lots of other butterflies out on the platforms, including
"Painted Lady, American Painted Lady, Red Admiral, Buckeye, Question Mark, CloudlessSulphur, Little Sulphur,
Ocola Skipper, and Many-banded Dagger Wing."
Bob adds, "In the moth department, we saw massive offshore movements of several species of hawkmoths (also
called sphingid moths or sphinx moths) during the Oct 7-12 post-frontal period. Pink-spotted Hawkmoths have been
most abundant, followed by Tersa Sphinx and Mournful Sphinx, plus a few vagrant Esso Sphinx." And to provide
further food for birds, "Dragonflies continue in force: Green Darners, Wandering Gliders, Spot-winged Gliders,
and Black-mantled Saddlebags have been joined by Red-mantled Saddlebags and a few Marl Pennants."
Can you find any of these insects in a field guide? Which ones can be found where you live?
Discussion of Challenge Question #7
Last week we asked why Dave Evans marks owl flight feathers with a permanent marker, and how long these
markings last. Second Grader Paul Mowery, in Nicole Long's class in Clarinda, Iowa, said, "I think that they
use permanent markers so the markings won't wash off when rain falls." Permanent markers can last through
rain and even sunlight as long as the feathers last. But hawks lose their flying feathers one by one, growing a
complete new set roughly every year so the feathers will always be strong.
Beth & Lorraine Colford-Feckter do a great job of explaining. "He marks the wing feathers to help in aging
the owl the next time it is caught. If the saw-whet owls molt their wing feathers in a certain order and the bird
is caught again, they will be able to tell how old it is. The permanent marker lasts until the owl molts the feather."
How to Respond to Today's Challenge Question:
1.Address an e-mail message to: jn-challenge-fall@learner.org
2.In the Subject Line of your message write: Challenge Question # 8
3.In the body of the message, answer the Challenge Question.
The Next Journey South Update Will Be Posted on October 30, 1998
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