Summer Breeding Grounds

Every spring, tens of millions of birds make the trek to their summer breeding grounds. Your smart bird feeder cam may pick up on these visitors, as you suddenly see a whole new crop of birds at your feeder. Warming temps and lengthening days prompt birds like warblers, thrushes, orioles, and flycatchers to soar north and begin one of the most critical parts of their lives—breeding.

But what exactly happens when these long-haul flyers reach their destinations? when they reach these summer breeding grounds? This blog provides a peek into these seasonal rituals and includes five fascinating facts about the biology and behavior of birds during this busy time of year.

A Bird’s Summer To-Do List: Nesting, Singing, and Courtship

Summer’s short, and that’s especially true for migratory birds. There are no carefree days for migratory birds–their hours are packed with three main goals: claiming some territory, finding a mate, and raising young. All of this has to be done before they head south again in the fall.

  1. Establishing territory: Male birds are often the first to arrive at summer grounds. They quickly stake out a territory that hopefully has a good mix of food, shelter, and spots to nest. They’ll often sing loudly from treetops or shrubs to warm off rivals and let potential mates know that they’re in the hood.
  2. Courtship displays: The elaborate courtship displays get underway once the females arrive in the breeding grounds. Depending on the species, these can be aerial displays or the construction of intricate nests–something to help a female judge the male’s fitness and rearing traits. Most species, but not all, find a mate at the breeding grounds–some paired the previous year or paired at their non-breeding grounds.
  3. Nest building: Birds construct nests using what they can find locally, including twigs, grass, and feathers. Location varies by species, and can be in trees, on the grass, in buildings, or in tree cavities.
  4. Egg laying and incubation: Females lay anywhere up to 10 or more eggs. Incubation lasts from about 10 days to about 20 days, during which one or both parents need to stay in the nest to keep the eggs warm; they stay in the nest the majority of the time once all the eggs in the clutch are laid, and stay longer and longer as the incubation continues. The type of nest can also vary by species.
  5. Feeding and fledging: Once hatched, altricial baby birds grow quickly. As they do, parents make dozens or more trips per day to feed them. After a few weeks the babies are ready to leave the nest but continue to lean on their parents while they learn how to forage and avoid predators. Check out Fact 5 below to learn about species that are almost independent from birth.

5 Fascinating Facts About Migratory Bird Breeding Season

  1. Some birds go for two rounds or more: If conditions are favorable, some species may raise two or three broods in one summer to up their chances of reproductive success. They can build more nests if one of the earlier broods was unsuccessful.
  2. Migration and breeding depend on climate cues: Generally, the length of the day and temperature trigger migration and breeding. A difference of just a few days can mean the difference between success and failure if a food source like insects emerges too early or too late.
  3. Birdsong is competition: It’s music to our ears, but for birds, the complexity and frequency of a male’s bird song reveal clues about his health and the quality of his territory.
  4. Kisses: As with most birds, hummingbird mating takes just a few seconds. In a process termed the “cloacal kiss,” they briefly touch their cloacals–an all-purpose digestive, urinary, and reproductive opening–to transfer sperm
  5. Early departures: Some precocial chicks, including species like ducks, turkeys, and cranes, leave the nest within just a few days. The killdeer chick, for example, can walk and feed itself within just a few hours of hatching.

The summer breeding season is a whirlwind of activity for European migratory birds. From the moment they touch down, these avian travelers are driven by instincts honed over millennia to ensure their genes are passed on. Whether you're an avid birder or a casual observer, paying attention to their behaviors—courtship dances, tireless feeding, or territorial songs—can offer a fascinating glimpse into one of nature's most impressive survival strategies.

So next time you hear the dawn chorus or spot a busy parent bird flitting through the trees, remember: there’s an entire drama unfolding above us every summer—one worth watching.