I had seen some photos of an “aberrant” swallow that had been spotted in the park recently so, when I visited on May 31, I kept my eyes open. The Least Bittern decided to keep a very low profile that morning and the last day of the Whimbrel Watch was quiet. While waiting, I noticed a swallow perched on a tuft of reed with unusual colouring in the area where the bittern had been seen (pic 1).
There had been speculation that this female-type bird was a cross between a Barn Swallow and a Bank Swallow, a case of delayed moult, or even partial leucism.
While I was photographing the bird, a male Barn Swallow flew in and perched on the same Phragmites stem and launched into his love song while slowly sidling up the stem, getting closer and closer. This bird obviously had no issues with hybrids or moults or lack of pigment—he sang and sang. Our unusual swallow looked spectacularly uninterested and eventually flew off (pic 2).
After a weigh-in by experienced birder Alvaro Jaramillo, he suggested that this was a female Barn Swallow, possibly in her first spring, with a case of delayed moult. He wrote, “This is what they tend to look like in winter down in South America, with short tails, mainly white underparts, and variable amounts of paleness on the face”. He thought it strange that she had not yet changed to a brighter plumage (pic 3).