One thing I always wonder when I see birds flying around cities is “where are they nesting???” Fortunately, the Audubon Society has an answer for that question – many birds nest in and on buildings and other anthropogenic structures. For example:
- Chimney swifts nest inside of chimneys
- Cliff swallows build mud nests on the sides of buildings
- Eastern phoebes, American robins, and house finches all find suitable nest sites underneath anthropogenic structures like ledges, porches, and decks
- Kestrels and barn owls will find their way inside of buildings to build nests on ledges and rafters
- Raptors like peregrine falcons seek out ledges in high places
- Pigeons will build their twig nests on elevated flat surfaces
- Starlings will find their way into a more protected site, like gutters and dryer vents
- Sparrows will find the nooks and crannies of any structure, tree or building, for their nests
- Gulls and killdeer are commonly found nesting on flat gravel roofs
This last point is intriguing. What are seabirds doing on top of buildings?! A reader of this blog sent us the following video that answers this very question. Check out this great compilation of urban yellow-legged gulls (Larus michahellis) growing from egg to subadult over the course of 8 minutes, created by Gonzalo Mucientes. Gonzalo tells me that the video was filmed in Pontevedra (Galicia, Spain). The film’s narration is in Galician, but the images speak for themselves (if you’re curious what it says, I’ve provided a rough translation below the video). In the video we see all sorts of interesting behavior: nesting, feeding, curiously inspecting the camera, and taking their first flight.
We’ve previously posted about gulls altering their behavior and flight patterns in urban areas, and the effects of human food consumption and habituation in Darwin’s finches. Gulls are typically ground-nesting species – so how does nesting on top of a building affect them? Some thoughts on this:
- Ground predators can’t access the nests, which means predation pressures on nests on top of buildings likely differs. Does this shift in predation type/intensity alter selection pressures on hatchling growth and development?
- Urban gulls are likely consuming large amounts of anthropogenic food (although they may shift their foraging strategy when nesting, as previous research has shown). What effect does anthropogenic food consumption have on the developing birds?
- The video shows the hatchlings rushing to their parents at the sound of a feeding call. Does anthropogenic noise impact this interaction?
- The video also shows an injured hatchling at one point. How do injury rates and types differ in urban gulls?
- Lastly, at the end one of the hatchlings takes to flight off the edge of the building. This seems pretty different from taking to flight from the ground. Does this result in higher probability of injury?
Check out the video and let us know what other questions you have after watching. And thanks to Gonzalo for sharing with us!
Translation of subtitles:
“On the Roof”
Cities are centers of cement and iron where you can find thousands or millions of people living. But these cities can provide habitat for wildlife. A yellow-legged gulls (Larus michahellis) is a marine bird that breeds on the Galician coast, preferably on islands. Sometimes they choose to breed in cities, building their nests on roofs.
After laying eggs, normally three, the pair take shifts incubating them. The eggs take 30 days to mature, and their success depends on the conditions of the year. Being a colonial bird, territoriality is a key issue. Males and females are practically indistinguishable, although the male is bigger and more robust.
Taking care of the chicks is the primary interest of the adults. The care and protection of the parents is constant. The chicks begin to ask for food by pecking at the red dot on the parent’s beak. The esophagus of the adult is already noticeably full, and it regurgitates partially digested food. The parent divides the pieces between the chicks, and they swallow it eagerly. The chicks follow their parents wherever they go. Their survival depends on this instinct.
Their cryptic plumage allows them to blend in with the vegetation. The chicks roam around, exploring their surroundings with innate curiosity. The chicks are covered in feathers from the time they hatch. This natal plumage plumage is a good thermal insulator.
They run quickly to respond to the calls of their parents. The heat makes them find refuge from the sun. The call to eat is loud and clear.
The growth is clear in the following weeks. The curiosity is a common element of the first stage of development. The beak is their tool for exploration with which they test everything they find.
A secretion falls on the camera – it is from salt glands that are located on the head. These glands secrete excess salt ingested in water and food.
Although cities seem more safe, the gulls are not free from suffering accidents. The gulls are now two months old, and they practice their first terrestrial movements. Their feathers are now ready for their first flight.
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