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468 Hand-Rearing Birds

Cuckoo Breeding Habits
There are Old World and New World cuckoos. Many Old World cuckoos are considered to be true
brood parasites. New World cuckoos, especially those breeding in North America, are not consid-
ered to be true brood parasites since they build their own nests and will raise their own young, at
least most of the time. They are themselves occasionally parasitized by Brown‐headed or Bronze‐
headed Cowbirds and Black‐billed Cuckoos (Hughes 2015). The YBCUs breeding behavior seems
to be modified by the abundance of food. They do not start breeding behavior unless there is an
adequate food supply available, so the exact month in which they start breeding may vary. In years
when food is very plentiful, the female YBCU may dump some of her “extra” eggs in another
cuckoo’s nest after her nest is completed or sometimes in the nest of another species of bird.
Apparently, this only occurs if there an ample food supply readily available, which seems to stimu-
late extra egg production in the female.
Both female and male YBCUs participate in nest building, incubation, and feeding of their
young. The nests are a rather flimsy open oblong cup design, loosely made from twigs, rootlets,
dried leaves, and pine needles. Eggs are sometimes laid before the nest is completely finished, in
which case the male continues to bring in nesting material to the female to finish the nest. One egg
is laid per day and clutches usually contain two to four eggs.
There are conflicting reports whether YBCUs have only one brood or two broods per year, and
where and how high the nest is placed. Some studies say nests are placed as low at 2 ft. off the
ground or placed up to 20 ft. high or even higher at 90 ft. off the ground. Reports of such varied nest
height placement may be due to habitat location or loss since they have nested across the U.S. in
various habitats.
YBCU chicks mature very quickly. Incubation starts with the first egg laid, so the birds may
hatch on different days. Hatch weight varies from 8.5–10 g. The naked birds can hold their heads
up to be fed almost right after hatching and can open their eyes and stand usually the next day.
Although born naked, they start to develop feather sheaths within 24 hours which will quickly
grow long and burst into to fluffy feathers (all at once) in about 6–7 days. They quickly learn to
perch on the edge of the nest, and between day 7 and 9 become “branchers” that can run along a
limb to greet a parent for food and do not return to the nest. It will take about 3 weeks after hatch-
ing before the young birds can truly fly and be independent (Preble 1957; Potter 1980).
Nesting cuckoos are very sensitive to disturbances, especially during pairing or nest building. If
an active nest has too many disturbances, reports of nest abandonment are common. Nothing is
known on whether cuckoo chicks can be “re‐nested” and the author would advise against trying.
Other cuckoo chicks may be put at risk of abandonment by human presence while trying to find
the nest or placing a bird back in the general area. Fledgling YBCUs move away from their nest
location, so returning a “healthy fledgling” to the same location where it was found is probably not
a good idea since they are not self‐feeding and are dependent on their parents for food for several
weeks after leaving the nest. The adults may have left the area with their other fast‐growing fledges.
It is not known if they are “good” parents and return to feed chicks that may be left behind, like
some species do.

Wild Diet
YBCUs feed heavily on caterpillars, including hairy caterpillars. They are known to eat insects,
especially katydids, cicadas, dragonflies, moths, flies, beetles, grasshoppers, ants, and other bugs.
YBCUs also have been seen eating small lizards, frogs, raspberries, mulberries, grapes and other
berries, small fruits, and the eggs of other birds.