A Northwoods Almanac for May 25 – June 7,
2012
Life Cycle of Ticks
I
think we say this every spring, but the ticks seem – how shall I say this
– abundant! Our dog had at least
50 on her after a hike in the Harrison Hills on 5/5. After you handle that
many, every itch you have feels like a possible tick!
“Know
thy enemy” said the ancient Chinese general Sun Tzu, so here’s what
seems to me to be important to know:
Since deer
ticks (Ixodes scapularis) are the ones that transmit Lyme disease, let’s focus on them. Deer
ticks live two to three years and have three blood meals. The life cycle
begins when the female lays upwards of 2,000 eggs, which hatch anywhere from
May to September. Each individual larva is the size of a period at the end of a
sentence, and initially does not carry Lyme disease. However, it may pick up
diseases during its first meal if the host, usually a white-footed mouse or
other small mammal, is infected. The larva then becomes infected and can
transmit these organisms during its second or third feeding the following
years. However, if the tick feeds on an uninfected small mammal or bird, these ticks
cannot transmit disease.
After
this first feeding, the larvae molt into nymphs and become dormant until the
following spring. In the spring and summer of the tick’s second year, primarily
from May through early July, the
nymph becomes active and takes its second feeding from a mammal. If the tick is
carrying disease agents from its first feeding in the larval stage, it can
transmit them during this second feeding. If the nymph was not infected
the previous year, it can become infected now if the second meal host is
carrying disease agents.
The
nymph is about the size of a poppy seed. Nymph stage ticks often look like a
speck of dirt or a freckle on a person’s skin.
In
the fall of the second year, the nymphs then molt into adult ticks. Adults are reddish-brown and about 1/8-inch long (or about one-half the
size of the more familiar female wood tick). The female is larger than the
male, and though the male ticks may attach, they
do not feed or become engorged.
The
adult female then feeds on large animals, primarily on deer, and then lays eggs the following spring. If the female
doesn’t get a blood meal by the end of the fall, she goes dormant over the winter
and seeks a meal in the spring. A frost does not kill deer ticks. Adults
may become active as soon as it is above freezing and may even be spotted
during a temporary thaw in the winter.
Deer ticks (and
wood ticks) wait for host animals from the tips of grasses and shrubs (not from
trees). When brushed by a moving animal or person, they quickly let go of the
vegetation and climb onto the host. Ticks can only crawl; they cannot fly or
jump.
Deer ticks are dependent on the white-tailed deer population for reproduction.
Larval and nymph stages feed on birds and small mammals, but the adult female
tick needs a large 3-day blood meal, usually from a deer, before she can
reproduce and lay her eggs. Deer are the primary host for the adult deer tick
and are key to the reproductive success of the tick.
Numerous
studies have shown that abundance and distribution of deer ticks are correlated
with deer densities. For example, when the deer population was reduced by 74%
at a 248-acre study site in Connecticut, the
number of nymphal ticks collected at the site decreased by 92%.
The
relationship between deer abundance, tick abundance, and human cases of Lyme
disease was also well documented in Mumford Cove near Groton,
Connecticut.
From 1996 to 2004, the deer population in
Mumford Cove was reduced from about 77 deer per square mile to about 10 deer
per square mile after focused hunting, which was enough to reduce by more than
90% the risk of humans contracting Lyme disease.
Remember: if a deer tick is infected, it must be attached for 24 to 48
hours before it transmits Lyme disease. The best defense is to check
yourself for ticks thoroughly every morning and night.
Relatively Quiet Birding
Mary and I led two bird hikes on 5/12 and 5/13
in the Lakeland area, and I co-led two other bird hikes on 5/18 and 5/19 on the
Apostle Islands. The birding was rather slow, a surprise given that mid-May is
THE time for seeing maximum numbers of songbirds. Many warblers appear to be
heading straight for their nesting territories. Bird researchers are finding
warblers back on territory a little ahead of schedule, likely due to the
advanced leaf out. Weather patterns have also not been conducive to large migratory
movements. Much of the month has been dominated by high pressure. There have
been few of the good Gulf of Mexico lows that come in from the south or
southwest and bring a major wave of migrants.
Still, during the Chequamegon Bay Birding and
Nature Festival on 5/17,
Ryan Brady reported 22 species of warblers at Bark Point (west of
Cornucopia) on Lake Superior, including close-up looks at a singing Connecticut
warbler, a species often very difficult to find. He noted that there were not a
lot of individuals, but lots of diversity.
The total tally for the event reached 176
species, around the average number they have found in previous years. Because
Chequamegon Bay offers such an amazingly diverse range of habitats – from open
farmlands to small towns to vast wetlands to the Apostle Islands – their
festival tends to record many more species than we do at our local festival in
Manitowish Waters. For instance, on one hike on 5/19, they found 17 species of
shorebirds – we just don’t have shorebird habitat at all comparable to Lake
Superior, though we did see long-billed dowitchers at the Little Turtle Flowage
on 5/13 (see the photograph by Juan Fernandez). The Chequamegon event also runs
over 100 activities across three days, so there are a lot more eyes and ears
out there counting birds.
Still, bird festivals really aren’t about
seeing maximum numbers of birds. They’re more about the joy of being in
beautiful places, feeling connected to the natural world, and sharing that
pleasure with other like-hearted people – the birds are just part of the total
experience.
Sightings
5/4: Grace Wanta
on the Turtle-Flambeau Flowage near Springstead reported seeing mallard
duckling and Canada geese goslings.
5/5: Sue DeFrancisco in Minocqua
wrote, “Cinco de Mayo was a 'fiesta' of a day for our
feeders ... one ruby-throated hummingbird, three red-winged blackbirds, and
five rose-breasted grosbeaks.”
5/7:
Peter and Carolyn Dring reported their first-of-year checkerspots, a subfamily
of butterflies, in the Land O’Lakes area, and a painted lady butterfly the next
day.
5/7: Carne
Andrews observed myrtle, chestnut-sided,
and magnolia warblers on the Lumberjack Trail.
5/8: Marlane Rasmussen
on Upper Springstead Lake reported her first-of-year ruby-throated hummingbird
as did Pat Schmidt, Missy and David Drake near Presque Isle, Uwe and Cathy Wiechering in Arbor Vitae, and Audrae Kulas.
5/9: Carne
Andres reported her first-of-year Baltimore oriole near Boulder Junction.
5/11: Bob
Bridges on Papoose Lake near Boulder Junction observed a red-headed woodpecker
being chased by a yellow-bellied sapsucker.
5/11: Louise
Church also spotted a redhead woodpecker in Hazelhurst.
5/12: Judith Bloom on Lake Tomahawk reported her first-of-year
indigo bunting. She also checked the loons on Lake Tomahawk, and found the nests of
five of the six pairs. All five are on nest, and Judith noted that this was
early and hopefully means that the black flies will not bother them this
year. Last year only one chick fledged on Lake Tom – the average is
five. Judith asked that I remind everyone to please stay 200 feet away
from any loons and their nests, and to obey “slow no wake” signs everywhere as
nests can be where you least expect them.
5/13: Mary
Henkel in Harshaw reported a pair of orchard orioles – a rare species in our
area – as well as two pairs of Baltimore orioles, visiting feeders at their
home on Little Bearskin Lake.
5/13: Peter and
Carolyn Dring reported Jack-in-the-pulpit and nodding trillium first in bloom
in the Land O’Lakes area.
5/17: In Mercer, a fawn and doe were
sighted walking across a pasture, a relatively early date for the appearance of
fawns.
5/21: Mary and I saw our first bobolink on Powell
Marsh.
Celestial Events
For planet-watching in June, look after
sunset for Mars and Saturn, both in the southwest, and Mercury low in the
northwest. Before dawn, look for Venus low in the northeast by mid-month and
Jupiter also very low in the northeast.
June
1 offers us 15 hours and 30 minutes of daylight – fabulous!
Look
for the full moon – the “Strawberry” or “Rose” moon – on 6/4. A partial lunar
eclipse will occur that night, though in Wisconsin the moon will set well
before mid-eclipse. We will observe a deepening shadow creeping left to right
across the lower portion of the moon. The eclipse begins at 3:38 a.m., and the
moon will set at 5:18 a.m.
On
6/5, Venus will transit across the face of the sun, an event that won’t occur
again until 2117, which I doubt too many of us will be around for! Called “The
Black Drop,” Venus will sail across the sun for over three hours, creating a
visible small black notch in the sun. The transit begins at 5:04 p.m. and
continues until sunset at 8:45, only partially making its way across the sun
before it sets.
Viewing
the transit through binoculars will enhance the event for you, but to protect
your eyes you must use proper filters such as an
astronomical solar filter, eclipse viewing glasses, or Grade 14 welder’s glass.
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