A Northwoods Almanac for October 13-
26, 2017
Snapping Turtles
Hatching
David Moyer
sent me photos of hatchling snapping turtles climbing out of their nest near
St. Germain on 9/25, a date that would seem late for snappers to still be
hatching. However, snapper eggs typically hatch after 90 to 120 days depending
on the soil’s summer warmth and moisture, so hatching usually occurs in
September in this area.
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| photo by David Moyer |
The
quarter-size hatchlings dig out of the nest and somehow know to head straight
for the nearest water, an ability likely associated with their highly evolved
sensory organs. Snapping turtles have extremely good eyesight both above and
under water and can even see straight above their heads because of the position
of their eyes. They also hear very well, and anecdotal accounts suggest
snapping turtles also have an extremely good sense of smell. So, perhaps they
can hear or smell water, which may account for their beeline to water.
The fact that these eggs hatched is
remarkable in itself. Only about 14% of all clutches emerge annually, the nests
destroyed by mammalian predators like skunks, raccoons, mink, and red foxes. An
undisturbed nest in a good year can produce up to 50 hatchlings, but still only
about 15 hatchlings will leave a successful nest (emergence success is only
about 20 to 45%). After
beating the heavy odds to even hatch, predation on the hatchlings is heavy,
especially during the first year, and only slightly lower during the 2nd and
3rd year, as raccoons, mink, weasel, skunks, herons, and large fish consume
them while they are still under three inches in length. Thus, the probability
of survival from egg to adulthood is 1 in 1445 individuals, while the
probability of survival from hatching to adulthood is 1 in 133. Female snappers
are most susceptible to an early death, leading to a probability of death between
hatching and breeding age of 99.17%. Annual recruitment (the number of
juveniles reaching maturity in any given year) into the breeding population of
males and females is only 1 to 1.8%.
Soil temperature determines the sex
of the hatchlings, males occurring more commonly after cool summers, and
females more prevalent after warm summers.
The hatchlings and juveniles live
apart from the adult turtles in small streams with very shallow water, up to 20
inches deep, where they can reach the surface while standing on the bottom. The
hatchlings and juveniles struggle to move against a current and are thought to
slowly make their way down into deeper lakes as they mature into adults.
While some adult snapping turtles
are still moving around at the beginning of October, they all move to their
hibernating areas by the middle of the month. Hibernating sites must offer
access to either dissolved or atmospheric oxygen, and must be deep enough so
the turtles don’t freeze to the bottom.
Each body of water only offers a
few premium sites for hibernation, so many snapping turtles literally hibernate
in a pile together, and often stack directly on top of each other with the
males on top of the females, perhaps to protect the females from both predation
and thickening ice.
Adult snappers have no natural
enemies (other than human morons who purposely kill them on roads), so they
usually live a long life and die of old age during the winter. Confirmed annual
adult mortality is only about 1%, which means that 60% of the individuals
reaching maturity will live to age 50.
Sightings
Denise Fauntleroy sent me photos of a pair of gray jays
that have appeared in her yard near Watersmeet, MI, and whom she is now feeding
to try to keep them around.
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| photo by Denise Fauntleroy |
White deer are relatively common in our area, but seeing
one is always a treat. Sarah Krembs sent me a photo of a doe eating crabapples
off a driveway near Manitowish Waters.
Jim Swartout sent a photo on 9/23 of a Tennessee warbler
that hit one of his windows in Minocqua and revived shortly thereafter.
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| photo by Jim Swartout |
Since the breeding range of Tennessee’s is restricted
almost entirely to the boreal forest zone of Canada, this bird was a late
migrant heading for its wintering grounds in Central and northern South
America. Some have suggested that the species would be more appropriately named
“coffee warbler,” because of its strong affinity for wintering in coffee
plantations in Central America. Recent studies have affirmed the importance in
particular of shade coffee plantations for Tennessee Warblers, yet another
reason for coffee drinkers to be sure to only buy coffee that is shade-grown.
As many as 150 species of birds utilize shade-grown coffee plantations. Modern
“sun” coffee plantations, planted after clear-cutting tropical forests, harbor
few wintering birds.
Sue Stanke in Park Falls sent me photos of painted lady
butterflies that were feeding on asters near the Fifield post office. And we’ve
had numerous painted ladies nectaring on asters in our yard as well. What is
remarkable about painted ladies is that they are migratory, and their journey
rivals that of monarchs. Painted ladies are found throughout much of the world, except for
South America and Australia. A 2014 study found that most European populations appear to
undertake long-range migratory flights to tropical Africa, thus crossing the
combined hazards of the Mediterranean Sea and the Sahara Desert. If butterflies
truly are making that flight in one generation, they could be traveling more
than 2,400 miles – a potential record for a migratory insect.
Green darner dragonflies have also been migrating south
since late August and may not finish their migration until late October. Thanks
to radio telemetry, we know that these dragonflies,
which weigh about one gram, can migrate over 400 miles. Professional hawk
counter Frank Nicoletti at Hawk Ridge in Duluth documented common green darners
migrating down the North Shore of Lake Superior, providing food for migrating
kestrels and merlins who also migrate during the early fall. Some green darners
are also non-migratory, laying eggs in summer that hatch out as larvae and
overwinter underwater.
Robins have been migrating through in large numbers. The
hawk counters on Hawk Ridge in Duluth counted 11,391 robins alone on 9/28.
Witch hazel, perhaps our latest flowering shrub, is still
in flower and will remain in flower well into November.
Tamaracks are coming now into their full smoky gold
color, an event I always look forward to every Octdober.
Celestial Events
On 10/17, look for Mars, Venus, and crescent moon grouped
together in the pre-dawn sky. The new moon occurs on 10/19.
In the pre-dawn of 10/21, look for the peak Orionid
meteor shower. The Orionid meteors radiate out from Orion, the Hunter. It’s a
modest shower, averaging around 20 per hour.
On 10/23 and 10/24, look after dusk for Saturn near the
waxing crescent moon.
We’re down to 10 hours and 29 minutes of daylight as of
10/23.
To view the International Space
Station, go to https://spotthestation.nasa.gov/sightings/ and type in your town to get exact
times and sky locations.
Finch Forecast
Ron Pittaway, an ornithologist in
Ontario, produces an annual “Finch Forecast” that we birders scour in hopes
that Canadian birds will be showing up at our feeders this winter. The cone
crop in the Northeast “is the best cone crop in a decade or more,” says
Pittaway, which means most winter finches will stay north. One of our favorite
winter birds, bohemian waxwings, look like they’ll stay north, too, because the
mountain ash berry crop is excellent. On the other hand, common redpolls and
pine siskins may be more abundant because of poor birch and alder seed crops.
As usual, time will tell, and species reports will be locally specific
depending on where the food is most abundant.
I’m glad it’s still hard to predict
bird populations and movements. A little mystery combined with a little
randomness makes for a deeper appreciation.
Thought for the Week
“The universe is a unity, an
interacting, evolving, and genetically related community of beings bound
together in an inseparable relationship in space and time. Our responsibilities
to each other, to the planet, and to all of creation are implicit in this
unity, and each of us is profoundly implicated in the functioning and fate of
every other being on the planet.” – Thomas Berry
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