FreeLists / va-richmond-general / [va-richmond-general] Re: Robins & Berries

["Carol Heiser" <cheiser@xxxxxxxxxxxxxxxx>]

Welcome to Richmond, Jody!  I think many of us have noticed the increased 
flocking behavior of robins recently, it is one of our earliest indicators that 
spring is coming.  Robins, redwing blackbirds, grackles, and other species 
typically begin congregating in mid- to late winter.  This behavior correlates 
with their annual seasonal movements from region to region; it's analagous to 
early migration but on a more regional basis, sometimes only state to state, 
sometimes from the south to the mid-Atlantic, etc.  Because of the high energy 
costs associated with this peak demand in activity, the birds must feed "more 
actively" to meet the need.  It is believed that species which assemble in 
large social groups, like seagulls on the beach or the robins you observed, 
have developed this behavior because it conveys an advantage to survival.  The 
theory goes that the more eyes there are to find food, the more likely that a 
large portion of the population will succeed to pass on their genes.  (It also 
means more eyes to see predators.)
 
As for the berries, there are several factors that influence when and what a 
group of birds will eat.  Most wildlife species are "opportunistic" feeders, 
that is they will take advantage of a food source if it presents itself and it 
is something the animal will eat.  In mid- to late fall there is (usually) an 
abundance of berries, seeds, nuts, and other food items.  Not surprisingly, 
that time of year is when birds feed more heavily to put on fat for the winter. 
 Over the winter months they rely on this stored fat in their bodies to tide 
them over while they eat any supplemental food items they can find.  Some food 
items have more food value than others.  For example, the berries on an eastern 
red cedar are preferred to those on a pyracantha bush, presumably because the 
former conveys more nutritional value.  As food becomes increasingly scarce 
towards the end of winter, birds (and other wildlife) begin to forage on "less 
desirable" items (kind of like food in the fridge--I'd rather eat leftover 
chicken than peas, but when the chicken's gone, it's either peas or nothing).  
This partly explains why birds might not eat pyracantha berries in fall but 
might eat them in very late winter.  Palatability also plays a role, since some 
berries need time to soften over winter.  But I have seen waxwings polish off a 
holly tree in early fall, not just in late winter.  So it could be a 
combination of factors, that your holly tree became a beacon to the flock which 
was scouting around for late season food, and the birds may not have fed on it 
earlier because the berries on that individual tree might not have been 
palatable until now.
 
By the way, there are several good books available about plantings for 
wildlife.  A recent one is Trees, Shrubs, and Vines for Attracting Birds, by 
Richard M. DeGraaf (2nd ed., revised), c. 2002, University Press of New 
England.  In general, when you provide a diversity of food, water and cover 
sources for birds, you "automatically" provide habitat for many other species.
 
Carol A. Heiser
Habitat Education Coordinator
Va. Dept. of Game & Inland Fisheries
4010 W. Broad St.
Richmond, VA  23230
phone (804) 367-6989
fax (804) 367-2311
cheiser@xxxxxxxxxxxxxxxx 

>>> j.taggart@xxxxxxxxxxxxxxxx 02/02/03 01:21PM >>>

Hi Everyone,

I moved here last July and have been on the mailing list enjoying the
information and stories others have posted. I wanted to tell you about an
interesting thing here.

When we moved into this subdivision I was disappointed about the lack of
trees in our yard. We  moved to a much smaller yard than we previously
owned. But the one good thing in the yard is a 30 ft. holly tree outside my
kitchen window. Being from the north I had never seen a holly TREE -only
shrubs.

So this beautiful tree has grown lovely red berries and it was so full that
the branches have been hanging lower than usual. Refilling the feeders in
the yard I wondered why the berries hadn't been eaten yet.

Friday I came home with the kids to find hundreds of Robins in the yard
going crazy eating the berries. Less than 24 hours later there was not a
berry to be found. Of course there is alot of evidence of all the berry
eating everywhere....

We saw several Cedar Waxwings as well.. one of my favorites.

Is it the ripeness of the berries that prompted the feeding? Or maybe the
birds just finally found the tree?

I haven't found time to visit many other birding spots except for Meadow
Farm and Three Lakes so if anyone has recommendations I would love to hear
them.  I live near Virginia Center Commons.

Jody

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