PITTSBURGH – How can two birds that look nothing alike come from the common ancestor? That was the question in my mind while observing the Shaft-tailed Finch and the Gouldian Finch. I observed these two birds at the National Aviary in Pittsburgh. They live in the Grasslands Room, a comfortably mild habitat with natural light, filled with the songs of birds. Many people describe a sense of calmness when they enter the room. A colorful bird perched on a low branch was the first to catch my attention. It didn’t look like any other bird in the room. It couldn’t be related to any of these other birds, right? Wrong.
The colorful bird I noticed was the Gouldian Finch. It’s covered in multiple blocks of color. Another bird I observed, the Shaft-tailed Finch, only had a red beak and red legs. Despite being so different on the outside, these two birds come from a familiar ancestor. Let’s look at the similarities and differences between these two:
Shaft-tailed Finch & Gouldian Finch Similarities
- Size – Sparrow sized birds
- Habitat – Northern Australia
- Both care for young
- Diet – Mostly seed eaters
- Clutch size – 4 – 7 or 8 eggs
- Plumage (feather) color and pattern – (see pictures)
- Sexual Dimorphism – Male and female Gouldian’s look different than each other.
- Diet – Shaft-tailed Finches will eat insects. Gouldian’s will not.
- Habitat – Woodlands (Gouldian) vs open grasslands (Shaft-tailed)
- Sexual Maturity – Gouldian’s = 6-9 months, Shaft-tailed’s = 9-12 months.
- Lifespan – Gouldian’s live 5-6 years in the wild, Shaft-tailed’s live 7-10 years
So, how could two birds that came from the same ancestor be so different? There could be multiple reasons. The most prominent being their habitat. The Shaft-tailed lives in open grasslands. Their dull colored plumage, other than their red beaks and legs, is optimal for camouflage in grasslands.
In contrast, the Gouldian Finch’s bright colored plumage is what’s best for their own habitat. They live in the woodlands of Northern Australia where they like perching in Eucalyptus trees. Further evidence that their color is due to their habitat is that Gouldian’s come in three main morphs or variations. There are red-headed Gouldian’s, black-headed Gouldian’s, and yellow-headed Gouldian’s. Planet Aviary’s Paul Bancroft has explored how habitat once separated these three variations into three most northern tips of Australia. The yellow-headed Gouldian’s lived in the Western Australia tip. The red-headed Gouldian’s lived in the Northern Territory tip. The black-headed Gouldian’s lived in the peninsula of Queensland. The three variations came back together after the expansion of the Savannah.
Bancroft noted the three morphs are still currently mixed together in the wild. Black-headed Gouldian’s make up about 70% of the population. About 30% of the population is made up of the red-headed Gouldian’s. Pulling up the rear are the yellow-headed Gouldian’s with about 1% of the population.
Sometimes there aren’t complex reasons for ancestors looking different from one another. Sometimes it just comes down to species blending in to their environment.