Many birds molt during summer's "down time" between raising their young and fall migration. At this point their feathers have worn out.
However (news to me!) female peregrine falcons choose a different time of year. They begin to molt during incubation, a convenient time to do it because they're temporarily sedentary and their mates supply their food. That's why we sometimes see a peregrine primary feather in the nest box. Who knew!
To become baby birds, eggs must be warmed to around 98.6 °F and remain at that temperature while the embryos develop. Adult birds that incubate(*) have special equipment to accomplish this: bare skin on the belly called a brood patch.
We don't usually see the brood patch because surrounding feathers close over it to keep the adult warm. When a bird comes back to its nest to incubate, it opens its belly feathers to lay its bare skin against the eggs. You may have seen peregrines open their belly feathers by standing over the eggs and rocking side to side.
Click on the link below to see an American kestrel's brood patch and learn about this important part of bird anatomy, the Brood Patch.
(*) p.s. In eagles and peregrines, both sexes incubate so both have brood patches but this isn't the case with all birds. In many duck species, only the female incubates so the males don't have brood patches.
Here's amazing news: Seabird colonies help keep the Arctic cool.
Seabirds gather on Arctic islands to breed during the summer. Thousands of them nest close together and produce a lot of guano (bird poop).
Atmospheric scientists studying the Arctic noticed summertime bursts of ammonia-based particulate. These tiny particles cause clouds to form because they gather moisture as they move through the air. The clouds reflect sunlight and keep the land and water cool.
Where does the ammonia come from? It wafts off the guano at the seabird colonies.
Canada geese challenge their enemies by honking and rushing forward with head low, mouth open and tongue raised. Normally we humans don't see this up close but a goose challenged David Amamoto and revealed its amazing tongue to the camera.
Since Canada geese don't have hands, their mouths are equipped with the tools they need for plucking grasses, sedges, grains and berries on land and in the water.
Their bills are serrated for cutting stems and threshing grain. Their tongues have serrated edges for sieving water from each mouthful of underwater food. The tongue's crosswise bumps help grip the vegetation.
As I mentioned on Monday, thousands of crows are back in Oakland roosting near the University of Pittsburgh. Though the flock is spectacular they'll soon be unwelcome.
If your neighborhood hosts a crow roost you know about the unpleasant debris left behind by these overnight visitors. Everything is dotted with bird poop. The sidewalks are slippery in the morning and the air smells "bird-y." This fallout is the #1 reason why crow roosts aren't welcome near us.
When people have had enough, the crows must go. The best way to move them is by persistent audio harassment.
In November 2013 the crows caused trouble night after night near the University of Pittsburgh Student Union so Maintenance set up a loud speaker that played bird distress calls and peregrine attack sounds over and over. In five nights the crows were gone.
I have a theory that my favorite bird helped move them. Read why at:
Jet airplanes cruise at 30,000 to 40,000 feet. Did you know that birds can fly at the low end of that range?
Birds' respiratory systems are so efficient that they can pull oxygen out of very thin air. We know this because they migrate over the Himalayas.
Common cranes (Grus grus) are widespread across Europe and Asia, nesting from Norway to Siberia and wintering from Africa to southern China. Those that nest in eastern Kazakhstan and northwestern China fly over the Himalayas to spend the winter in India. They've been clocked at 33,000 feet!
Bar-headed geese (Anser indicus) nest in the Tibetan highlands and spend the winter in the lowlands of India. The shortest route from Tibet to the sea is to fly directly over the Himalayas, and so they do. They've been recorded at 29,600 feet and seen flying over Mount Everest! This video shows how they do it.
And even mallards, the ubiquitous ducks that eat bread at the boat launch, were seen migrating at 21,000 feet over Nevada.
Birds don't need oxygen masks at those high altitudes. They just fly by.
(photo credits: All photos are Creative Commons licensed via Flickr. Click on each image to see its original:
View from a jet over the Himalayas by David C. Jones on Flickr
Common cranes in flight by Ján Svetlík on Flickr
Mallards in flight by Ken Slade on Flickr
Video from FantasticAnimal on YouTube)