Just before Christmas, two backyard birders in Michigan were in for the ultimate surprisea yellow Northern Cardinal. Arlene and John McDaniel spotted the incredibly rare bird in their backyard in Bath, Michigan near East Lansing.I really couldnt believe it, Arlene tells Popular Science. We do get a lot of cardinals. Theres always a lot here. The males are just a stunningly beautiful red and females are more orangey, But when we saw this yellow one, the thing that really made it distinctive, other than its feathers, is that its beak is also yellow.Arlene and John McDaniel spotted this yellow cardinal in their backyard on December 23, 2024. CREDIT: Linda Vail. Both musicians, John says they named the bird Donovan in homage to the folk musician. His catchy tune Mellow Yellow reached the number two slot on the Billboard Hot 100 in 1966.Heres what you should know about these beautiful birds.How rare are yellow Northern Cardinals?While previous sightings of these birds have garnered the phrase, one in a million, there is no solid data on just how rare these canary-colored cardinals are in the wild.It is hard to get a sense of just how rare yellow Northern Cardinals are, and there does not seem to be any study that estimates the frequency of this plumage aberration in the general population of cardinals, Cornell University ornithologist Shawn Billerman tells Popular Science. But, given that Ive been birding for close to 30 years and have never seen a yellow Northern Cardinal, it is safe to say they are pretty rare.Why arent they red?Genetic mutations that alter pigments in an animals feathers, scales, or hair are typically behind strange colorings in animals. Sometimes these pigments are either not expressed or are overexpressed, which results in some rare changes in the color.We do not seem to know the exact genetic mutation that causes yellow-pigmented Northern Cardinals, but whatever the mutation is affects the birds ability to produce red carotenoid pigments, explains Billerman. All carotenoid pigments, most of the bright yellows, reds, and oranges that we see in birds plumage, including those of the Northern Cardinal, come from the diet, but the red pigments in a cardinals plumage are metabolically derived and synthesized from the carotenoids they acquire from their diet.[ Related: One in 100 million cotton candy lobster caught in New Hampshire. ]A 2003 study analyzed the feathers of an individual yellow Northern Cardinal. This specific bird lacked all of these reg pigments that were derived from what it had eaten. The authors believed that the unknown genetic mutation present in this bird disrupted the metabolic pathway that helps the body synthesize red carotenoids. The enzyme that converts the carotenoids from the birds diet into the red that is seen on feathers was likely not present.At least in the individual they studied, they also identified some yellow pigments that were metabolically altered, so the bird did not lose all carotenoid metabolic functionality, but it was just unable to create the red pigments typical of the species, says Billerman.An unknown genetic mutation affects Yellow Northern Cardinals like Donovans ability to produce red carotenoid pigments. CREDIT: Linda Vail. How are they different from other cardinals?While ornithologists are still learning about yellow Northern Cardinals, it does not appear that they differ from more typical red cardinals. However, Billerman says that the mutation that prevents them from synthesizing red pigments might affect others aspects of their lives.Some evidence does suggest that the redder and brighter male Northern Cardinals have both greater reproductive success and held larger territories.If red coloration is indeed an important factor in mate choice or breeding success, it may be possible that this yellow Northern Cardinal has a harder time finding a mate, says Billerman.The post Extremely rare yellow cardinal flies into a Michigan backyard appeared first on Popular Science.