Figure
Legends
Figure 1a: An American robin (Turdus migratorius ) ground-nest in
the incubation stage. To human observers, the nest is well-camouflaged
against a litter substrate but the bright blue eggs are readily visible
when the incubating female is not present. This stands in contrast to
typical tree nests early in the season, which are readily visible to
human observers (inset). Photo credit: M. Hauber.
Figure 1b. A robin ground-nest in the nestling stage. Four nestlings are
present in the nest cup, which sits in a small depression in the ground.
The rim of the cup is built-up mud and grass like an arboreal robin nest
and extends <5 cm above the ground. Photo credit: S. Winnicki.
Figure 2. The twenty-two ground nests (red-shaded curve) for which we
could estimate laying date were initiated early in the breeding season,
in April and May. This constrasts with the 185 tree nests from 2019
(blue-shaded curve), which were initiated from April and May into June
and July.