Geoscience Reference
In-Depth Information
minor
) of Australia and New Zealand, as well as the Magellanic penguin (
Sphenis-
cus magellanicus
) of southern South America, also excavate burrows.
Inallinstances,birdsusetheseburrowsfornesting.Nonetheless,burrowsalso
havethegreatmulti-purposeadvantageofprotectingchicksandadultsfrompredat-
ors while providing a place that maintains a near-constant temperature year-round.
The latter especially comes in handy in high-latitude environments, where trying to
stay warm during wintertime without shelter could quickly sap energy reserves.
Because birds do not have shovels, nor arms well adapted for holding shovels,
they must use a combination of their beaks and rear legs to excavate a burrow. Ima-
gine carrying out a mouthful of sediment at a time or scratching with your feet to
make a tunnel many times longer than your body: like
The Shawshank Redemption
,
but without even the benefit of a little rock hammer. These burrows are not just
tubular, either, but also expand at their ends to include a nesting chamber. These
chambersmustbelargeenoughtoaccommodateeggs,chicks,andatleastoneadult
to tend to the eggs and feed their offspring, which have the annoying habit of grow-
ing bigger with multiple feedings.
An important point to know about burrowing birds, however, is that they may
reuse or steal burrows, then—like squatters taking over a house—remodel and oth-
erwisemodifythemtosuittheirownneeds.Forexample,burrowingowlsmaytake
over appropriately sized mammal or gopher-tortoise burrows. Rough-winged swal-
lowsmightusurpkingfisherburrows,andvice-versa.Somebirds,though,maytreat
their burrows more like vacation homes, coming back to them at certain times each
year. A male-female pair of Atlantic puffins, which normally mate for life, might
return to the same burrow they used the previous year for nesting, then do some
home improvement to prepare the nursery for their next brood. If the old burrow
collapsed or otherwise is in bad shape, they may dig a new one. Because puffins
are quite sociable, their togetherness results in huge colonies; this means they dig
manyburrowsandmanygenerationsofburrows,whichoftenintersectwithonean-
other, making for massive composite traces below ground. Complicating these un-
