Reports from the 1996 NABS Conference in Ontario
BIOMONITORING WITH BLUEBIRDS
At the Ontario NABS meeting William (Bill) Read introduced us to the new
idea of using bluebirds as monitors on the effects of agricultural chemicals.
A half-day field trip to some of the many commercial apple orchards in Ontario
was not only enjoyable, it opened up a whole new area of bluebird research
that Bill, Martin K. McNicholl and Chip Weselolz have been doing for the
Canadian Wildlife Service. The service is promoting Canada's Green Plan,
a highly commendable national effort to monitor a wide variety of chemical
contaminants in wildlife. Technical Report Series no. 202, Ontario Region
1994 makes fascinating reading, not only on the research itself, but on
observations on the life, biology and reproductive success of eastern bluebirds
in Ontario. Copies are available from: Canadian Wildlife Service, 867 Lakeshore
Rd, Box ,505n, Burlington, Ontario, L7R 4A6. Canada.
The survey covered 100 responses representing 101 trails. 72 of the trails
had been in existence since 1080, with an increase of 53% in the last five
years. Tree swallow nests greatly outnumber those of bluebirds in all areas.
(Boxes were not paired).
Some interesting facets: the trails which had existed for more than 15 years
had double the fledging rate ( 1.14 young per box) than newer trails (.15
young per box). Also of note was that larger trails (more than 50 boxes)
consistently produced a higher fledging rate than smaller trails ( 1-20 boxes).
There was little difference in fledging rate between trails one to five years
old and those six to ten years old. Blowflies were the single most important
nest-loss factor, with wrens a very close second. House sparrows were the
third most common cause of nest failure.
Bill Read is working with the Agriculture Ministry in an Environmental Farm
Program to ascertain the neurotoxic effects of organophosphates on bluebirds
and tree swallows by placing nest boxes in commercial apple orchards. By
monitoring population trends, reproductive success and behavior of bluebirds
arid swallows. the neurotoxic effect of organophosphates on birds can be
ascertained. Possible changes in behavior, hatching success, feeding of young,
the number of times young call for food, etc, is being measured. Surprisingly,
preliminary studies of bluebird boxes placed in sprayed apple orchards indicated
that there seems to be no decrease in reproductive success attributable to
the chemicals sprayed on the apple trees. ??
BLOWFLY RESEARCH
Apropos to the findings of Bill Read that blowflies were the foremost cause
of nest failure in Ontario, research done by Chris Darling, Curator of' the
Royal Museum, was also presented al the NABS meeting. Particularly interesting
was the implication that nest box design might be a factor in attracting
blowflies. (A 1982-85 study by B.C. Pinkowski in Michigan showed that there
were twice the number of blowflies in artificial nest boxes than in natural
tree cavities.)
There are ten species of blowflies, two of which are attracted to bluebird
nests, and are most virulent in eastern bluebird boxes. Blowflies, like many
other insects. give off special scents, called pheromones. to attract the
opposite sex. Would altering the airflow in a nest box attract less blowflies?
Would reducing airflow also dissuade the jewel wasp (Nasonia vitrepennis)
which parasitizes blowfly larvae?
Large screened openings at the nest level were made. with the thought that
the concentration of attracting pheromones would be reduced. The concentration
of blowflies and wasps proved to be not significantly changed.
Screen platforms (actually hardware cloth) placed under the nest did seem
to reduce the number of blowfly larvae sucking on young bluebirds by about
25%. It also increased significantly the amount of parasitism of blowfly
larvae (under the screen) by the wasp. Darling and coworkers also found that
bluebird nests constructed of pine needles had no blowflies.
More research needs to be done. In answer to a question about whether old
nests should be thrown out in the fall, Chris Darling advised that nests
should be thrown out deep in the woods. rather than on the ground near the
box. This procedure makes it more likely the parasitic wasp eggs which may
be in the nest will survive the winter. When the nest is left in the box,
the wasp eggs and larvae probably would not survive. (One blowfly cocoon
can hold 40-50 wasl eggs. )
Ed.s note: The efficacy of the screen platform has been debated; raising
the level of the nest can increase risk of predation if boxes are not mounted
to deter climbing predators.
Use of chemicals such as Flys Away II were not considered in the above
study.
