Answer Archive

Question from Nina (St. Paul) on March 30, 2016:

“What is the cause of the rust color on the neck and heads on the tundra swans?  I observed a migrating flock on March 27th near Hastings MN and the color was quite pronounced.”

Robin Maercklein: The rusty or dark coloring on the necks of swans is caused by tannins in the water where they feed. Often the shallow water where they feed will have lots of decaying vegetation on the bottom that releases tannins. This in turn stains the feathers of the birds that feed in those areas though it is most evident on birds with white heads and necks!

Brian Collins:swan The rust color comes from their feeding habits.  Both Tundra Swans and Trumpeter Swans feed by tipping up into shallow water and uprooting starch-rich tubers from the mud.  Many waters are situated over soils that produce a rust colored stain instead of just making for muddy feathers.  The repeated action of rooting through the mud eventually stains the feathers.  Sandhill cranes uproot plants and mud and deliberately smear it over their gray feathers, adorning themselves with rust colored plumage by Spring.   Compare the feather colors of freshly molted cranes in the autumn versus cranes in the spring for the full effect of this behavior.  In some locations, such as the Vadnais Lake area in the Twin Cities, I have observed groups of swans completely lacking in the rust staining. I suppose that is because the lakes do not freeze and the swans spend most of the year there…and the mud is not the staining sort.  Nonetheless, the behaviors of the swans are the same, rooting in the mud day in and day out for rich, nutrient aquatic plants.  This swan foraging behavior also serves as a reminder to our vigilance in conservation, as drought years can expose swans to lead sinkers and old lead shot, contributing to increases in cases of severe lead poisoning.   To me, a rusty-headed swan is tell-tale to the most wild swan, inhabiting areas rich in northern sedge meadow, bog lands, acidic outflows, and iron-rich, and tannin-rich water tables associated with “north country”.

Question from Jan (Barron, WI) on January 7, 2016:

“What are the small sparrow sized birds I see alongside the road in winter?   They are in a flock usually gathered where the snow has melted away, when approached they fly up  giving the appearance that they are white underneath.”

Robin Maercklein: The two most likely flocks of sparrow like birds alongside the road at this time of year are American Tree Sparrow and Dark-eyed Junco. If it’s juncos, look for the white outer tail feathers that flash as they fly. Other less likely possibilities include Purple Finches and Common Redpolls.

Brian Collins: atsp-troy-jan-6-2013-img_2309I agree completely with Robin. American Tree Sparrows tend to leave the road and retreat immediately to roadside brush or weedy hedges.  On quiet, rural roads, if you can safely stop and observe their retreat, you can see the American Tree Sparrows as they lurk in the brush, a few eventually perching in clear view.  Listen for their soft, “teedle-ee” calls coming from the brush. Dark-eyed Juncos have that bright, white flash of outer tail feathers. When finches such as redpolls leave the road, they often head upward and will perch higher up in order to survey for danger… This time of year, you are also likely to see huge flocks of Snow Buntings around open fields.  When they fly, they give the appearance of a snow flurry, with black and white patterns flashing.

Click here to send us your questions!