ScienceDaily (May 14, 2012) — A male robin will be more diligent in caring for its young if the eggs its mate lays are a brighter shade of blue.
The blue colour in robin eggs is due to biliverdin, a pigment deposited on the eggshell when the female lays the eggs. There is some evidence that higher biliverdin levels indicate a healthier female and brighter blue eggs. Eggs laid by a healthier female seemed to encourage males to take more interest in their young.
Kiwis are flightless birds endemic to New Zealand. They are the smallest ratites (flightless birds) in the world and lay the largest egg in relation to their body size of any bird species currently living. There are five recognized species, all of which are currently endangered due to habitat destruction and invasive/introduced mammalian predators.
The Sulawesi Cuckoo (usually referred to as the Sulawesi Hawk-Cuckoo, but more related to the Typical Cuckoos) is endemic to Sulawesi Island, in Indonesia. Like the other Cuckoos, this species is what’s known as a brood parasite. While a nest is unattended by the occupants, they’ll come in, lay an egg, and leave. This is then repeated with several other nests in the area, until the clutch is laid. Depending on the species, the adult cuckoo may eject the occupant’s eggs prior to laying her own, or the cuckoo chick may eject its nest mates once it hatches.
Because the chicks of brood parasites are larger and hatch earlier than the host’s eggs, they divert all attention from the host’s eggs. Birds (passerines especially) are pretty much “hey there’s a screaming chick, better feed it”, so little songbirds sometimes end up caring for and raising these big ol’ cuckoo chicks without knowing something’s off. Or maybe they do know and just can’t do anything about it, but who am I to tell? Host birds are at least clever enough that if a female cuckoo lays her egg in the nest of a bird that has differently-colored eggs from her, they other bird typically ejects the cuckoo egg and lays another clutch of her own.
Transactions of the Zoological Society of London. 1874.
ScienceDaily (Dec. 2, 2011) — When it comes to choosing their wintering destinations Antarctic skuas are flexible. This is shown in a study of an international research team led by the polar-ornithologist Dr. Hans-Ulrich Peter from the Friedrich Schiller University Jena (Germany). According to the study, a great part of the South Polar skuas spend the Antarctic winter in the Northern Atlantic. At the same time about one third of the same species overwinters in the Northern Pacific, tens of thousands of miles away.
ScienceDaily (Nov. 29, 2011) — Pointing and holding up objects in order to attract attention has so far only been observed in humans and our closest living relatives, the great apes. Simone Pika from the Max Planck Institute for Ornithology and Thomas Bugnyar from the University of Vienna, however, now provide the first evidence that ravens (Corvus corax) also use so called deictic gestures in order to test the interest of a potential partner or to strengthen an already existing bond.