On Thu, 14 Mar 1996, Patricia Tucker Stroh wrote:


> So as not to make my first posting too long (though it probably already
> is!), I'll just close here with a question from last year's pied-billed
> grebe nesting season. There were about 14 nests along the west side of the
> lake, most within about 15 feet from shore. The northernmost nest was
> constructed--and reconstructed and reconstructed--by two grebes who never
> seemed to get it right. They must have laid 8 separate clutches of 1-2
> eggs, none of which lasted longer than about 2 days. In two winters of
> grebewatching (perhaps 30 nests or more), they're the only pair I've seen
> fail.
> How do grebes learn how to build nests, anyway? I assume part of
> their knowledge (or guesses) comes from watching their parents do their
> constant repairing and replenishing of the nest after the young are born.
> But they would never have the chance to witness the building of a new nest
> from scratch. The two grebes in question seemed not to understand that
> they had to choose fairly buoyant material to keep the soggy nest from
> sinking right away--or at least that's how I interpreted the problem. Any
> ideas? Is there genetic programming involved? Why would these guys get it
> wrong when everyone else gets it right?
>
> Trileigh Stroh
>
> Department of General Science
> Seattle University
>

Hi Trileigh,

Nest building behavior in birds does not involve any learning at all, in
the sense of watching and imitating, as far as I know. For one thing,
most parent birds do *not* refurbish the nest after eggs are laid, and
certainly not after the chicks are hatched and old enough to watch. For
another thing, birds raised from the egg in captivity exhibit mostly
normal nest-building behavior (I say mostly because captive raised birds
usually behave slightly abnormally in all respects, so I wouldn't be
surprised to hear that some of them build slightly weird nests). Birds no
doubt learn from experience where appropriate nesting materials are
easiest to find (e.g., feathers are commonly found at the edge of ponds
with ducks on them), but the decision about what constitutes "appropriate"
nesting material is mostly innate.

About all I know about grebe nesting behavior specifically comes from a
friend who studies Red-necked Grebes on their nesting lakes in Alberta.
He says that some Red-necks* build a new nest every day or two for the
whole season, only to have each one destroyed the same way, by
wind-generated waves. He says he wants to shake them and say "Think!!!!"
but the grebes keep trying the same exposed spot until it's time to
migrate again.

*please, punsters, resist!

If the Pied-billed Grebe nests are sinking without help from waves, then
it isn't exactly the same, but the two cases combined still suggest that
some grebes have trouble making any kind of adjustment when a nest fails.

Maybe even though most of the behavior is genetically "determined,"
birds can adjust the details slightly based on experience (except
grebes!). Or maybe lots of birds have these problems, but we only notice
in grebes, because they nest in conspicuous places. I know Mourning
Doves build pretty pathetic nests, and a fair number of them collapse
before the chicks fledge. I wouldn't know if it is nests from the same
individuals that are always collapsing, though.

Anyway, good post, keep up the reports! And I agree, Greenlake is a
great place to watch birds. The best looks I've ever had at Pied-billed
Grebes of all ages have been at Greenlake.

Chris Hill
Everett, WA
cehill at u.washington.edu