The Barn Swallow (Hirundo rustica) is recognized for its graceful flight and close association with human-made structures. This small, widespread species commonly builds its nest in sheltered locations, often choosing the rafters of barns, sheds, and garages. Understanding the eggs helps in identification and appreciation of the species’ reproductive cycle. This guide provides a look at the characteristics of Barn Swallow eggs, from their visual features to the timeline of their development.
The Distinctive Appearance of Barn Swallow Eggs
Barn Swallow eggs are identifiable among common backyard bird eggs. The base color of the shell is typically creamy white, sometimes appearing pinkish-white or a pale buff.
The eggs are speckled and spotted with darker tones, primarily reddish-brown, dark brown, and purplish-brown. These spots can also include shades of gray or cinnamon, creating a mottled effect that helps camouflage them. The markings are often more concentrated around the larger, blunt end of the egg. The eggs are ovoid or elliptical ovoid, meaning they are rounded at one end and taper towards the other. The surface may also exhibit a slight gloss.
Size and Typical Clutch Dimensions
Barn Swallow eggs are relatively small. The average length of a single egg is approximately 20 millimeters (0.8 inches), and they measure about 14 millimeters (0.5 inches) across at their widest point.
The number of eggs laid in a single nesting cycle, known as the clutch, is substantial. A typical Barn Swallow clutch ranges from three to seven eggs, with four or five being the most common number observed. The female usually lays one egg each day until the clutch is complete. Clutch size can be influenced by geography, with northern populations tending to lay a slightly higher average number of eggs.
Nest Context and Incubation Timeline
The eggs are found within the mud-cup nest constructed by the adult pair. The nest shell is built from numerous mud pellets gathered by both the male and female, often reinforced with grass stems. This structure is typically semi-circular when built against a vertical surface, such as a wall, beneath an overhang or the eaves of a building.
Once the mud shell is complete, the cup is lined with softer materials, primarily fine grasses and feathers, creating a comfortable environment for the eggs. The process of incubation, where the eggs are kept warm until hatching, usually takes between 12 and 17 days. The female typically performs the majority of the incubation duty, though the male may assist in short periods. After the eggs hatch, the nestlings remain in the nest for about 20 days before they are ready to fledge.