Page 182 - Hand rearing birds second

168 Hand-Rearing Birds

Figure 10.1 Foot of a Pied-billed Grebe chick.
Other grebe species often have reduced webbing
between the digits and stiffer toes overall. Source:
photo courtesy of Wildlife Rehabilitation Center of
Minnesota.

Grebes nest where they live, and build floating nests of cattails, grasses, and other vegetation in
freshwater lakes, ponds, slow moving rivers, estuaries, and marshes. They situate their nest where
thick vegetation grows out of the water, and a portion of the heat necessary for incubation is thought
to be provided by decomposing vegetation built into the nest (Muller and Storer 1999). There are
variations from species to species, but 3–10 light‐blue to white eggs are laid and incubated for
approximately 21–23 days for smaller species: Black‐necked, Pied‐billed, Horned, and Least; and
smaller numbers of eggs incubated for 25–28 days for larger species: Western, Clark’s, and Red‐
necked. Both parents cooperate to incubate and care for the young when they hatch. Hatch weight
also varies from species to species and ranges up to 30 g in Western Grebes (LaPorte et al. 2013).
Grebes are highly susceptible to breeding failure due to human disturbance on lakes by water rec-
reational vehicles, and nests may be left high and dry if the water levels of reservoirs drop during
breeding (Plumas Audubon Society 2016). Western and Clark’s Grebes are known to hybridize and
may produce young during fall or winter in southern regions (e.g. Southern California).
The semi‐precocial young are mobile, covered with dense down, and have their eyes open at
hatching; however, they require parental care for food, warmth, and protection from the elements
and predators. Hatchling grebes will spend most of their time during the first few weeks of life
nestled on their parents’ backs, with short forays into the water to drink, defecate, practice swim-
ming, and to learn how to forage for food. Parents share the responsibility of carrying the chicks
equally. When transferring duties, one parent will “dump” the chicks off their back into the water
only for the other parent to come and let the chicks climb onto theirs; dumping the chick into
water also stimulates the chick to defecate. The unencumbered parent will then forage for food and
offer it to the young grebes (LaPorte et al. 2013). It takes 6 weeks for hatchling down to transition
to juvenile plumage, with flight feathers coming in around 10 weeks of age. Grebes become inde-
pendent of their parents at about 8–12 weeks of age, depending on the species. At 6 months of age,
grebes reach 75% of their adult size and will find a mate and breed within 1 to 2 years of age.