Juvenile Barn Swallow
In late summer and early autumn, Swallows, or to give them their full name, Barn Swallows, can be seen and heard in large numbers, chattering away on overhead wires in preparation for migration.
The term Swallow is still sufficient to identify this bird here in UK, but nowadays with our more extensive travelling and knowledge of birds of other countries, the more specific name of Barn Swallow is often used. For example, another European swallow occasionally seen in the UK is the Red-rumped Swallow. Worldwide, however, there are 17 swallow species in the same genus as our swallow, Hirundo (means ‘swallow’ in Latin), as well as other swallows of different genera.
When the swallows gather on the wires, the juveniles can be recognised from adults by having a paler reddish throat and a shorter tail which extends to about wing-length (See attached photos). Adults have darker red throats and longer streamers to their tails, with males on average 18% longer than females.
In fact, the length of the adult male’s tail is important in its breeding success. Female swallows prefer to mate with males with longer tail streamers in the assumption that they will pass on better genes to their offspring. Swallows mate for life, though either sex will seek a new partner in the event they lose their existing one. The shorter tails in juveniles are considered by biologists to be very close to the ‘aerodynamic optimum’ for natural flight, whereas adult tails have evolved to greater length due to sexual selection.
These swallows migrate 6,000 miles all the way to southern Africa on a perilous journey over the Sahara Desert. Many birds unfortunately perish on route. Ironically, therefore, the juveniles could be considered better equipped aerodynamically to make this journey than their parents.
See more on their activities and photos or if you’re interested in joining below:
Facebook: RSPB Dorking and District
Instagram: @rspb_dorking
Website: https://group.rspb.org.uk/dorkinganddistrict/
Top image: Adult male Barn Swallow
