Laura Erickson - Into the Nest: Intimate Views of the Courting, Parenting, and Family Lives of Familiar Birds

When parents teach their children the facts of life, they often refer to the birds and the bees, even though birds and bees have entirely different equipment than mammals do and few people have the slightest idea how birds or bees actually do it. This book aims to shed light on the family lives of birds, a topic that has captured our collective imagination and enriched our language despite being shrouded in mystery.

Every species has its own approach to every aspect of reproduction: finding mates, claiming and defending territories (or not claiming one at all), finding or building a nest or other structure in which to deposit eggs, protecting and incubating those eggs (or finding another bird to do it in certain cases), and feeding, protecting, and educating the young. In some species, the reproductive process can last a few weeks from start to finish; in others, it lasts for longer than a year.

The processes of bird reproduction are so intertwined that its difficult to separate them out. For example:

• A male House Wrens territory and nest cavities are his primary ways to attract a mate.
• Herons include nest-building as part of courtship.
• Feeding a prospective mate during courtship helps prime an Evening Grosbeak to feed nestlings.
• Success or failure in rearing their young influences whether a pair of robins will stay together the following breeding season.

This book focuses on the varying ways some familiar species conduct their family lives. Evolution provided each species with different strategies, but in every case the goal, to produce new birds to carry on the parents genes, is the same.

A stick can be an integral part of courtship. A male Great Blue Heron offers a series of sticks to the female who, at a certain moment, will accept a particular one and then crouch, ready to mate.

A male House Wren sings to attract a female to his territory. If she likes one of the nest sites hes prepared, theyll mate and start a family.

Courting and Mating

Selecting the right mate is fundamental to a birds success in keeping its genes alive. Gaudy plumage, healthy feathers, lively singing, and energetic courtship displays play a role in helping females identify the strongest, healthiest males and, in some species, the best potential co-parents. Females often dont display obvious (to human eyes) signals of fitness, but a females responses to a males advances help him see how healthy she is and how well shell raise young.

Eastern Bluebird pair

Mate Fidelity

The fittest male hummingbirds mate with several females. Producing sperm is simpler and less physically taxing than producing eggs, so males may be less concerned than females about the fitness of a potential partner.

In other species, monogamy (one male paired to one female) is the norm. Male crows, swans, and geese commit for life to one mate, and so are as motivated as females to select the fittest mate available. In many species where pairs mate for life, the plumage of both sexes is identical, at least to our eyes.

In many species, such as owls, parrots, and these Rock Pigeons, preening the mate is an important part of courtship. This behavior, called allopreening, can help strengthen the bond between the male and female and synchronize them physiologically for breeding.

Far more species are serial monogamists. These birds pair for a single breeding season or raise one brood together and then find new mates to raise another brood that same season.

In the far north, where summer is brief, Bald Eagles must find a mate that will be physiologically synchronized with them almost as soon as they arrive on territory in spring. They must have enough time to produce fertile eggs and raise the young.

Rather than advertising a territory, as do wrens, robins, and blackbirds, birds of this species invest weeks, months, or even years in choosing a mate. Once they commit, they can count on that mate as long as they both survive. Those that remain together throughout winter start courtship behaviors during migration, so both birds will be ready for reproduction soon after they arrive.

Few eagle pairs remain together during winter, but both adults return faithfully to the same territory and nest every spring. Dramatic courtship flights and more practical behaviors, such as repairing the nest, help cement their bond and synchronize their hormonal levels. By returning to the same nest year after year, they dont need to rebuild from scratch.

Sky dancing, performed here by a pair of Bald Eagles, is an essential aspect of courtship, synchronizing hormonal levels.

Pairing for Life

Whether birds mate for life depends partly on whether both can survive the winter and find each other the following breeding season. The oldest known wild Bald Eagle survived more than 32 years, the oldest known wild Whooping Crane lived to be 28, and one Mourning Dove wearing a U.S. Fish and Wildlife Service leg band survived for more than 30 years. Even tiny birds can have surprisingly long lives: Black-capped Chickadees have lived longer than 11 years, and one miniscule Broad-tailed Hummingbird banded in Colorado was re-trapped, alive and healthy, 12 years later.

Despite their potential longevity, the overall mortality rate for many of these small birds is high, and most songbirds and hummingbirds cannot plan on their mate returning year after year. Some songbirds, such as American Crows and Florida Scrub-Jays, mate for life, often remaining on the same territory year-round. Only if their mate dies do they search for a replacement.

American Crows seem steadfast: they mate for life and often stay year-round on the same territory. They also build a community, maintaining relations with their young and neighbors throughout their lives.

Pairs of many songbirds, such as robins, remain together throughout a whole nesting season, raising two or more broods of chicks. Either or both adults may return to the same or a nearby territory the following year, but neither seems to expect to see their previous mate again; birds of these species often select a new mate each year.