St. Olaf College | Natural Lands

Fall and Feathers

Fall is here! The migration season is upon us, and there is no better time to look at all the unique
birds that fly through our campus! For anyone interested in joining bird watchers this season, this
article is the perfect way to dive in!

Speaking of diving in, let’s start with the waterfowl. The waterfowl–or, as we overworked Bio
majors call them, the Anseriformes–are one of the oldest extant bird families, with the oldest
known fossils going back to the late Cretaceous Period!1 Another sign of the group’s longevity
is that waterfowl are some of the few birds that have penises. Like all birds, waterfowl have two
layers of feathers. In the Anseriformes, the outer layer is waterproofed by oils that the bird
preens on, covering an inner layer of insulating, dry down. The structure of the down traps warm
air.2 Mallards, the most recognizable waterfowl in Minnesota, nest on the ground, sometimes
as far as a mile from water.3 Their relatives, the Wood ducks, nest in trees, and can be seen
flying through the woods far from water.4 The two species are also distinguished by their
heads, which are smooth in the case of the mallard, and adorned with what looks like a helmet in
the case of the wood duck. Everybody likes cute ducks, but everyone hates those noisy Canada
geese! But did you know that they might not even be Canada geese at all? That’s right! In 2004,
one population of these foul fowls, previously classified as a subspecies, was scientifically
described as Branta hutchinsii; the cackling goose (no doubt at us). In addition to genetic
differences, the cackling goose is on average about half the size of a Canada goose.5 One
question remains though; are cackling geese as obnoxious as Canada geese?

If so, head for the woods to escape their wrath and see the peckers! All woodpeckers–members
of the Picidae family–have four toes. The toes are oriented into an X formation, with two toes on
each side of the foot, an adaptation that helps them climb trees. Another cool feature is that
woodpecker tongues wrap around their heads! At up to a third of the bird’s body length, the
tongue is anchored in the nostrils and joined at the back of their skulls. It is believed that the
tongue also helps cushion the skull and keep it in place while pounding a tree.6 Those holes in
trees that wrap around the tree? Those are called xylem wells and are often made by yellow-
bellied sap-suckers! The red-headed woodpecker stashes acorns in its holes in fall and early
winter. Small, shallow marks along the tree indicate an area where the woodpecker was
searching for food. Woodpeckers have great auditory acuity and can hear things below the
surface of the bark that may indicate the presence of bugs. Woodpeckers will also sometimes
remove whole sheets of bark from trees!7

Woodpeckers make a number of different types of holes in search of bugs, but what about bigger
prey? Minnesota’s skies are crawling with raptors, so how can you know which one you are
running from? Raptors eyes have two sets of lids. In the inner lids, the nictitating membrane protects
the eye from debris, with piscivorous raptors shutting it but keeping the primary eyelids open as
they dive into water.8 In some species, the color of the eyes changes over time as they get older.
Diurnal raptors also have more color-detecting cells in their eyes, which increases the precision of their sight.9 Turkey vultures have a V-shaped wing posture, while bald eagles have a straighter wing posture with upturned tips. The osprey, a fish eater like the bald eagle and often a victim of being robbed at the claws of the latter, has a distinctively W shape to its wing posture. The falcons hold their wings forward.

What’s that? A fight with an eagle has started? It must be a murder of crows! This family of
birds is infamous for its feuds with the raptors. These bird brainiacs have been shown tool usage,
and have collective memory! But what is the difference between the members of this family
anyway? Crows are smaller than ravens, and inhabit open lands, while ravens are forest birds and
are bigger. Ravens also have more hoarse calls. Another open country corvid is the black-billed
magpie. Inhabiting northwest Minnesota, these birds are easily identified by their long greenish
tails, bluish wings, and white underbellies. These birds are also capable of mimicking the sounds
of various other animals, a trait which they share with crows and ravens. Blue jays are also
corvids, and often stash acorns for the winter. Some scientists even suggest that blue jays might
be keystone species in the development of oak forests.10 It might seem strange that a bird as
brightly colored as the blue jay would belong to a family of birds known for their dark plumage.
Should blue jays even be blue at all? Well, they aren’t! One of the amazing properties of feathers
is that they can create false colors with their structure! The structure of the feathers refracts blue
light but contains no blue pigment itself.11

Just like squirrels right? Darn, those squirrels just can’t stop messing up the bird feeders, can
they? Better learn about the songbirds in order to help them! Songbirds belong to the
Passeriformes, the biggest group of birds. The American robin was named for its resemblance to
the European robin, even though the two are not related (in fact, the American robin is a thrush).
Robins can sometimes be seen tipsy in late winter and spring after eating fermented berries.
Robin eggs–laid up to three times per brood season–are a bright sky blue.12 Robins make ‘tuk’
calls or ‘peek’ alarm calls. Cardinals make loud, two-parted whistles. Their eggs are white or
light blue with brown speckles. A fun fact about cardinals; a rare mutation causes some of them
to appear all yellow!13 Black-capped chickadees just go, well ‘chick-a-dee’. In northern
Minnesota, black-capped chickadees share their territory with the boreal chickadee.14 Boreal
chickadees have a redder looking back, and have less white and more gray. Black-capped
chickadee eggs are white with dark red speckles.

1 The Cornell Lab of Ornithology Handbook of Bird Biology. 3rd Ed., Wiley, 2016. P. 39

2 The Cornell Lab of Ornithology Handbook of Bird Biology. 3rd Ed., Wiley, 2016. P. 129, 114

3 Mallard Anas platyrhynchos., Mallard | Audubon Field Guide. 10/30/2023

4 Tekiela, Stan. Birds of Minnesota. 2nd Ed., Adventure Publications Inc., 2004. P. 148

5 Griffiths, Devon. Learn To Tell a Cackling Goose From a Canada Goose., Learn
to Tell a Cackling Goose From a Canada Goose | Audubon. 10/30/2023

6 Wang et al. “Why Do Woodpeckers Resist Head Impact Injury: A Biomechanical
Investigation.” PLOS ONE, Vol. 6, No. 10, October 26 2011, Pubmed, doi:

7 10 Types of Woodpecker Holes and other Woodpecker Signs on Trees., 10 Types of Woodpecker Holes and Other Woodpecker Sign on Trees
– Nature Identification. 10/30/2023

8 Birds Have Built In Goggles., 2018, Birds Have Built-In Goggles | Audubon.

9 What Makes a Raptor – Part 3, Keen Eyesight. University of Minnesota, 2020, What makes a
raptor – Part 3, keen eyesight | The Raptor Center ( 10/31/2023

10 Johnson, W. Carter. Webb, Thompson III. “The Role of Blue Jays (Cyanocitta cristata L.)” in
the Postglacial Dispersal of Fragaceous Trees in Eastern North America.” Journal of
Biogeography, Vol. 16, No. 6 November 1989, pp. 561-571, JSTOR,

11 Tekiela, Stan. Birds of Minnesota. 2nd Ed., Adventure Publications Inc., 2004. P. 64

12 Runwal, Priyanka. 10 Facts About the American Robin., 2020, 10 Fun Facts
About the American Robin | Audubon. 10/30/2023

13 Saha, Purbita. Why is this Northern Cardinal Yellow?, 2018, Why Is This
Northern Cardinal Yellow? | Audubon. 10/30/2023

14 Boreal Chickadee Poecile hudsonicus., Boreal Chickadee | Audubon Field
Guide. 10/30/2023