Swallows on Ten Mile Bridge
- Forward of a message from Erica Fielder
>> Yesterday, July 4, Larry Knowles and I took the canoe and paddled
>> the Ten Mile Bridge to count the cliff swallow nests that, as far as
>> could tell, were being used this year. We counted 1,185 of them.
>> Assuming that each nest is maintained by two adults and that there
>> also unmated individuals in the colony, we estimated there were close
>> to 3,000 birds involved, not counting chicks. We saw lots of little
>> heads peeping out of the entry spouts to the nests.
>> Over the 15 years I have lived at Ten Mile next to the bridge, I have
>> noticed that the swallows move, year to year, to different sections of
>> the bridge to make nests. Two years ago they nested on the northern
>> third of the bridge. last year, they nested on the southern third.
>> year they are nesting on the center third. I think they rotate to
>> reduce possible infection from disease, mites, lice, etc. You can see
>> thousands of old nests and parts of nests in the unused sections. I
>> expect that next year, the swallows will use the nests on the northern
>> third of the bridge, that is, unless CalTrans disturbs them too much.
>> think bridge construction begins in 2006.
>> To my surprise, the swallows built twice the number of nests on the
>> more exposed side than on the protected east side of the bridge. I
>> observed just the opposite in years past. Does anyone else have
>> information on this? Since the new bridge will be built on the east
>> side of the existing one, perhaps the swallows are already responding
>> to CalTrans disturbance. There has been some activity on the east side
>> over the years as CalTrans drills and explores the river.
>> After our count, we observed the birds for about an hour from the
>> on the south side of the river. A male kestral spent some time perched
>> on the telephone wire that hangs close and parallels the bridge. For
>> least 20 minutes he periodically flew beneath the overhang to the
>> nests and appeared to be looking into the nests. Sometimes he actually
>> landed and clung for a moment to the entrance of a nest. Once I saw
>> stick his head into a nest. During the time we observed him, he caught
>> nothing, but he sure looked like he was trying to grab a chick. During
>> this behavior, clouds of swallows followed him at a distance. They
>> never got close to him, like blackbirds would do. Even though these
>> nests appear quite protected in their position above the river, they
>> are vulnerable to both predators and humans.
>> I sure hope CalTrans has made adequate nesting sites with a flat,
>> vertical surface and an overhang so the new bridge can support this
>> huge population.
>> For more information on Erica Fielder Studio,
>> please see my two websites:
>> Erica Fielder Studio
>> P.O. Box 1075,
>> Mendocino, CA 95460
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