The willows are
budding which means, as every farmer knows, that the grass is growing.
Spring is finally here and I have noticed that with the warmer mornings
Piwakawaka, the fantail, is getting up early again.
I have been spending
a lot of time over the winter, watching the fantails or, more precisely,
worrying about them. How these tiny insect eating birds manage to survive
the winter is a constant source of amazement to me. Depending upon the
severity of the winter, many of course do not survive.
This has been a mild winter
so most of my birds here have managed to come through, whereas last winter
was very hard on them. Nor did they breed here last year very successfully
as it was cold and wet well into December.
But these wonderful little
birds have developed strategies to survive, not the least of which is the
ability, which theyshare with many other birds, to have several broods
the conditions are right so that even after a hard winter their numbers
can increase very rapidly. Another strategy it seems is to get up late,
very late, of a cold frosty morning.
Around here they are not
to be seen until after the sun has warmed the pastures and the little midges
they feed on are active again.
A third strategy is the
fantail's clever choice of sites to roost at night. The bush used
to provide dense warm cover for the forest birds before introduced deer,
pig and goats cleared away the understory. Now Piwakawaka has made its
adaptions and a favoured site for one pair here is a large pampas
bush growing on a hillside in the lee of the southerly wind, and
which gets the first rays of the morning sun. They tuck themselves deep
into this bush and only emerge when the sun rises. Another couple has found
a wonderful roost between the black polythene covered stacks of haysilage,
a spot that would be very warm indeed.
However, it is not just
fantails which take so much trouble in finding sites to roost at night.
What makes a good roosting site for birds? What influences their choices?
First the roost must provide
protection from predators when the bird is asleep and relatively unresponsive
to danger.
Many species roost in
dense cover, including some ground dwellers such as pheasants while
most hole nesting birds roost in holes. Other birds such as skylarks roost
in open ground, relying on spotting an approaching predator before it finds
them.
The second vital function
of a roost, especially critical for fantails, is to provide warmth and
shelter from the weather.
Fluffing out feathers
improves insulation but birds can alsoreduce heat loss appreciably by roosting
in some kind of shelter. Bushes, trees and other cover can help maintain
the body temperature by those few vital degrees. Some birdshave learned
to roost in towns where the average temperature may be higher than
in the countryside.
Though some birds such
as dunnocks and thrushes roost alone, many birds, from waders and
gulls to starlings, gather together at night in large communal roosts for
at leastpart of the year. Around here it is the sparrows and the
finches that roost together in favoured avocado trees, once again the trees
on a slope in the lee of the southerly winds.
They huddle together in
such roosts for warmth, the most dominant birds taking the centre positions,
forcing the immature and more subordinate to the edges where they are at
the mercy of the elements. Another advantage of communal roosts may
be to gain extra protection from predators, the chance being
that some birds will not be sleeping so deeply and can warn others,
The most intriguing idea
advanced by recent research to explain communal roosting is that in some
species, such as starlings, the roost may serve as an information centre,
enabling birds to share, among other things, information on better food
supplies.
So it will be interesting
to see if the idea grows and my fantails' trick of roosting between
the haysilage bales will be passed on to others of their kind.
