Birds have evolved many clever adaptations to protect their eggs from threats in the environment. One of the most remarkable is the ability of some bird species to shelter their eggs from hailstorms. Hail poses a serious risk to exposed eggs, with hailstones capable of cracking or destroying the fragile shells. Remarkably, certain birds have developed specialized techniques to shield their eggs when hail is imminent.
The Need for Egg Protection
Bird eggs are very vulnerable before hatching. Their soft, calcium carbonate shells can be easily crushed by impact from falling hailstones. Even small cracks in the shell can be detrimental, exposing the developing embryo inside to bacteria, drying out, or other threats.
For species that nest in exposed locations, hail is a major hazard that could wipe out an entire clutch of eggs. Some birds nest in tree canopies, while others lay their eggs directly on open ground. Without protective measures, a hailstorm could destroy all their hard work in brooding the eggs and preparing the nest.
Over time, evolution has shaped some incredible hail protection adaptations in certain avian parents. Species with the strongest defenses are those that experience hailstorms regularly in their breeding habitat. Their specialized egg-shielding behaviors and nest architectures help ensure the survival of the next generation.
Adaptable Nest Locations
One way some birds evade hail is by adaptability in where they place their nests. Birds have a range of preferences when it comes to nest sites, with habitat niches including cliff faces, tree branches, shrubs, caves, burrows, and ground scrapes.
Species that experience seasonal hailstorms may evolve to be highly opportunistic in their nest placement. They take advantage of whatever sheltered nooks they can find, rather than sticking to a fixed nesting site that could leave eggs exposed.
For instance, the barn swallow is known to be flexible on nest placement. A migratory species widespread across North America, it often builds its mud nests on ledges or beams inside barns and other structures. But if no suitable indoor sites are available, barn swallows will readily nest instead on cliff overhangs, dense shrubs, or other protective spots outside. This adaptability helps ensure their eggs stay safe from hail.
Some other birds that are nomadic nesters in response to hail threats include sparrows, wrens, and black phoebes. Their adaptability and mobility gives them better odds of raising their chicks safely through stormy breeding seasons.
Insulated Nests
Rather than moving their nests, some resourceful birds modify them to shield eggs from hailstones. One approach is to build an exceptionally thick, insulated nest that absorbs and distributes the energy of hailstone impacts.
A prime example is exhibited by prairie birds like the mourning dove. Its nest is constructed of tightly interwoven twigs, grasses, and stems up to several inches thick. The dense materials provide padding to cushion the blows from hail. The nest’s thick domed shape also helps deflect hailstones outward and away from the well-protected eggs inside.
Other creative nest insulators include chipping sparrows. They often add a roof or partial dome of pine needles above the inner egg chamber. And blue grosbeaks mix shredded bark, grasses, leaves, and other materials into a sturdy, hail-deflecting pouch nest.
Cavity Nesting
Another common adaptation is for birds to raise their eggs inside protective cavities. Nesting inside tree hollows, stumps, old woodpecker holes, rock crevices, or tunnels burrowed into ground provides a sheltered environment. The surrounding wood, soil, or stone acts as insulation against the impacts of falling hail.
Many songbirds utilize cavity nesting to escape hail, including chickadees, nuthatches, titmice, bluebirds, and tree swallows. Woodpeckers may also take advantage of their own excavated holes for breeding if hailstorms threaten. And burrowing owls and bank swallows nest in tunnels dug into dirt banks, keeping eggs out of harm’s way below ground.
Cavities provide such reliable protection that competition for prime nest holes is often intense. Birds may stake claim to a coveted hollow long before the breeding season starts. This ensures they have access to one of the safest nest types for enduring spring hailstorms.
Ingenious Nest Coverings
Certain birds don’t just rely on well-insulated or hidden nests. Some species take the remarkable extra step of actively covering their eggs when hail is imminent.
This egg-shielding behavior is most developed in grebes. These diving water birds build floating platform nests in shallow ponds and lakes. When storms approach, parent grebes respond by carefully covering their eggs with reeds, plant material, feathers, or their own bodies.
The feather coats of grebes are well-adapted for this task. Their chest plumage is less dense and rigid than in other waterfowl, allowing grebes to flatten down on eggs completely. Both parents often assist with brooding the eggs while splashing water over their backs for added insulation.
Time-lapse videos reveal the choreography of industrious grebes working together to pile nesting material high before a storm hits. They use this technique not just for hail, but also heavy rains. Species from horned grebes to eared grebes have all been observed actively modifying their open nests into protective egg bunkers.
Hail Protection by Birds Around the World
Birds utilize inventive methods of safeguarding eggs against hail across continents worldwide. Here are some remarkable examples from each region:
North America
– Killdeer: This widespread North American plover lays its speckled eggs directly on open ground in fields, gravel, or lawns. When hail threatens, killdeer parents use their bodies to hover horizontally over the nest. Their outstretched wings and tail may help shield the nest bowl beneath.
– Mountain bluebird: They build sturdy nest boxes out of abandoned woodpecker holes or manmade boxes. The tree cavity insulation protects their pale blue eggs from hailstone impacts.
– Burrowing owl: These small owls nest in tunnels dug into prairie dog burrows or other dry, flat ground. Their eggs stay safe from hail below ground level.
Central and South America
– Andean coot: This stiff-tailed water bird breeds around high-altitude Andean lakes. Their floating, domed nests anchored in rushes are heavily insulated with vegetation to protect eggs during hailstorms.
– Toco toucan: With their huge sawtooth beaks, these iconic toucans excavate deep nesting holes inside tropical rainforest trees. The thick interior wood helps shield their eggs from heavy damage by hail.
– Cave swiftlet: Flocks roost high inside caves across Central America. Their valuable edible nests are cemented under overhangs deep inside caverns. This perfectly protects the eggs from harsh tropical hailstorms.
Europe
– White stork: Iconic on rooftops across Europe, these large birds often place their oversized nests atop chimneys or spires. The nest’s broad, thick platform structure helps disperse hailstone impacts away from eggs.
– Eurasian nuthatch: They nest in old tree cavities lined with grasses, moss, and feathers. These cozy hollows provide good insulation from hail bouncing through woodland canopies.
– Northern lapwing: Also called the peewit, its mud-lined, shallow nest scraped into fields is notoriously difficult to spot. But the nest’s low position often provides a degree of shelter from wind-driven hailstones.
Africa
– Marabou stork: This unusual African stork nests high on bushy acacia trees during the rainy season. Their large platform nests have a partial roof that may help shield eggs from heavy hail.
– Superb starling: They nest in cavities including holes excavated by woodpeckers. The eggs and chicks are well-protected inside thick tree trunks and branches during storms.
– Ostrich: The largest bird in the world lays its eggs in simple scrapes on open savanna ground. But ostriches incubate the eggs buried beneath their own body feathers for protection from hail.
Asia
– Oriental white-eye: This tiny warbler builds a neat cup nest high in dense tropical foliage across Asia. The summits of their nests often feature a woven canopy to help repel jungle rain and hail.
– Edible-nest swiftlet: As its name suggests, these swiftlets build highly valuable bird-nest soup nests across seaside caves in Southeast Asia. The nest cups cemented to cave walls shield eggs from tropical coastal hailstorms.
– Indian skimmer: Their ground nests on sandbars and gravel beaches are very exposed. But parent skimmers shelter the eggs by covering them with their large black-and-white wings during hailfalls.
Australia
– Superb fairywren: This common Australian songbird builds a round, domed nest with side entrance. The sturdy grass structure offers extra protection against hail in coastal scrubs and woods.
– Malleefowl: This stocky ground-dwelling bird breeds in semi-arid mallee woodlands. The parents cover their nest mound with a thick “browsing shelter” dome to protect eggs from harsh outback hailstorms.
– Wedge-tailed shearwater: These petrel-like seabirds nest in burrows dug into soil on offshore islands. The underground egg chambers provide perfect shelter on islands frequented by hailstorms.
Egg-Saving Ingenuity
As these examples illustrate, birds around the world have evolved a diverse array of physical and behavioral adaptations to protect their precious eggs from hail. From thickly insulated nests, to cavity nesting, to actively sheltering eggs with their bodies, different species utilize their own specialized strategies based on their local environment.
This flexibility and ingenuity is key to their reproductive success and survival. By shielding fragile eggs from hailstone blows, diligent bird parents ensure the next generation hatches safely. Their carefully adapted nests and egg-covering behaviors are a remarkable evolutionary adaptation to dynamic climates and the ever-present threat of sudden hailstorms.
Conclusion
Birds need innovative solutions to save their eggs from dangerous hail. A variety of species worldwide demonstrate specially adapted nest designs, types, materials, locations, and parental egg-brooding behaviors to help minimize hail damage. From grebes covering eggs with reeds to burrowing owls nesting underground, different birds have evolved unique hail defenses based on their habitat and exposure to storms during breeding season. These special egg-protection adaptations provide key insights into avian resourcefulness, parenting devotion, and survival in the face of environmental extremes. They show that with the right ingenuity, fragile eggs can stay safe even in the most turbulent conditions.