Hi Jim -- they're probably tiny insects called "snow fleas" or "springtails"
which are very active on warmer days in winter. Small, but VERY abundant -
up to 300 million per acre in grassland habitats. They're not fleas, but of
an order called Collembola. A quick reference from North Carolina State
University offers:
Life History & Ecology:
The snowflea, Hypogastrura nivicola, is a dark blue collembolan that is
often found on the surface of melting snow in late winter or early spring.
The springtails are among the most abundant of all soil-dwelling arthropods.
They live in a variety of habitats where they feed as scavengers on decaying
vegetation and soil fungi. Most species are small (less than 6 mm in length)
and quite susceptible to desiccation unless they remain in a moist
environment. A unique, tube-like structure, the collophore is located
ventrally on the first abdominal segment of most species. The exact function
of this organ is unknown, but it probably helps maintain water balance by
absorbing moisture from the environment.
Springtails are named for a forked jumping organ (the furcula) found on the
fourth abdominal segment. The furcula is retracted against the ventral wall
of the abdomen and held there, in cocked position, by a special catch (the
tenaculum) on the third abdominal segment. Releasing the tenaculum causes
the furcula to snap down against the substrate and flip the organism some
distance through the air. This device, present in all but a few genera,
seems to be an effective adaptation for avoiding predation.
Immature collembola are similar in appearance to adults. They usually molt
4-5 times before reaching sexual maturity, and continue to molt periodically
throughout the rest of their life. Unlike most other arthropods, springtails
appear to have evolved in a cool climate. Their relative abundance in the
soil tends to increase as the mean annual temperature decreases and their
development is most rapid under cool, humid conditions.
_______________________________________________
Bob Hinkle
Chief of Outdoor Education
Cleveland Metroparks
11350 Broadway Ave
Garfield Heights, Ohio 44125
(216) 341-9225
Interpretation is a mission-based communication process that forges
emotional and intellectual connections between the interests of the audience
and the meanings inherent in the resource.
-----Original Message-----
From: Ohio birds [mailto:[log in to unmask]] On Behalf Of James
Dolan
Sent: Wednesday, February 21, 2007 11:27 AM
To: [log in to unmask]
Subject: [Ohio-birds] More Interesting Robin Behavior
Monday afternoon I got out for a walk in the woods. At one point
I observed a Robin walking on top of the crusted snow. The bird was busy
feeding on something, but there were no berry bushes or weeds around.
As I looked closer, I saw that there were small insects walking across the
snow. I don't know what kind of bugs they were,(I'm not an
entomologist). The Robin was actually eating the insects. The bird
would have to eat an awful lot of the bugs to get filled up. Has
anyone else ever seen this?
Jim Dolan
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