To our Sponsors and
Current hysteria in various media formats about the prevalence of
West Nile virus, in birds across eastern North America, has suggested
that we should issue a status report to members of the Owl Foundation.
The virus is indeed
here, as well as being everywhere else, and we have lost a number
of the total number of owls in all the 16 Canadian species we regularly
house. In some species, the deaths seem disproportionately high;
in others, inexplicably, there are no deaths at all. Theories abound
as to why losses are so unevenly distributed among species. Amid
the speculations, some facts stand out.
For instance, even
with 35 Screech Owls (mostly vulnerable juveniles in training for
release), we have lost none. The same applies to 2 Barn Owls and
10 Burrowing Owls. Of 10 resident Great Horned Owls, only one has
died. The four resident Barred Owls are still with us, only one
of four juveniles has succumbed. Eight resident Short-eared Owls
in one complex are intact; all our resident Long-eared Owls are
still here. Likewise all the Flammulated and Pygmy Owls.
On the other hand,
in our four Northern species - Snowies, Great Grays, Hawk Owls and
Boreal Owls, the death toll has been appalling. In trying to explain
the differences, we have to recognize precipitating factores in
the Northern species. One thing they all have in common is extremely
dense plumage. This makes them less attractive to mosquitoes (the
vector for West Nile Virus) but it renders them irresistible to
a hippoboscid fly, another parasite of wild birds. Our sponsors
may remember our ranting over the annual depredations of this cursed
fly in newsletter after newsletter. The fly requires a blood meal
to reproduce itself and it gets it in a curious way - by drilling
a little hole in the lower shaft of a developing feather, still
encased in nourishing blood. Enough of these "Flat Flies"
on a single owl can reduce its packed-cell volume (haemoglobin)
to dangeous levels. Action is required to remove the flies before
he dies of anaemia.
Last year we had
very few problems with these flies; this year is a different story.
Our winter was so mild it did not kill the pupae from the flies
which lie on the gound, then we had 6 weeks of rain in March and
April which prevented us from removing the pupae and covering the
ground with this cedar, then the weather was so hot in June and
July that the Northern species simply suspended normal functions
Our need to handle
the heavily feathered species for flat fly removal was the final
stress they could not handle. These three things; blood loss, extreme
heat and constant handling were inevitably the precipitating factors
that eroded immune function in these very shy and vulnerable owls
and opened the door of opportunity for a new virus. Unfortunately,
a compromised immune defense is not as easily demonstrated in histopathology
as the footprint of disease.
We clearly face three
imperatives if we plan to continue housing Norther owls. Firstly,
we need a vaccine against the new virus. We have already had 74
owls vaccinated, but the vaccine is new, its efficacy in owls is
unknown and its applicaiton was probably several weeks too late.
Secondly, we have
to find a solution to the flat fly problem. This is the tough one.
We need innovative help from agricultural and veterinary communities
- not only for the sake of future owls but also to look at the fly
as a new potential (if only mechanical) vector for viruses like
West Nile. After all, the mosquitoes that access blood from skin
and the flat flies that only drink from feathers, both can transport
blood. We need chemicals that neutralise the pupae on the ground
under our cages to prevent emergence of the next generation of flies.
Thirdly, we must
build an isolation ward of 16 to 20 units to control access of either
mosquitoes or flies between birds that are arriving at the Foundation
or those that are under suspicion. We needed it this past dreadful
summer and work will commence on it this fall.
It is important to
us that our members understand the present situation and recognize
that all attempts to salvage damaged wild lives and make them productive
again, can be viewed as a mine-field with no map. Some people think
it is useless to try; others, like the staff of the Owl Foundation,
feel that humans made the mess and it is bloody well up to us to
do something about it. We hope you will agree and that you will
continue to support us as we stumble on, looking for solutions.
Yours most sincerely,
President, The Owl Foundation