By Lucca Sterrer of University of Vermont
Walking through the rich forests of Southern Patagonia, it is not uncommon to be approached by one or a few of these brightly colored, curious little birds. Thorn-tailed Rayaditos (Aphrastura spinicauda) are around 13-14 cm in length with a very distinct orange and black “thorn”-tail. The Spanish name, Rayadito, translates to ‘striped’, most surely referring to the thorn-like feathers in the tail that develop in the birds as they mature. An average adult Rayadito weighs around 10-13 grams, with the males typically weighing ten percent more than the females.
These birds are endemic to Patagonia and were first discovered on Tierra Del Fuego, a group of islands off the southernmost tip of South America. They reside mainly in southern temperate forests or locally arid lowland scrub. Round River Conservation Studies has seen many Rayaditos in its day. They were spotted on most (if not all!) of the research transects that we completed this semester. Thorn-tailed rayaditos are easy to observe because they’re not only common to the area we’re studying, but they’re also very inquiring creatures! When they hear unprecedented loud noises, their first instinct is to investigate! Often times, when we were walking in big groups through Lenga (Nothofagus pumilio) and Nirre (Nothofagus Antarctica) forests, a group of Rayaditos would slowly make their way through the treetops towards us to see what all the commotion was!
Due to their common diet, Rayaditos can also often be seen with white-throated tree runners (Pygarrhichas albogularis). Rayaditos have a main diet of arthropods, and like the birds they are commonly compared to, the tits of the northern hemisphere, Rayaditos spend most of their time searching bark and other mossy surfaces for smaller insects to eat. Below there’s a picture of a Rayadito enjoying a worm that he found (Figure 2)!
The mating season for Rayaditos is during the Austral spring and summer (February through April). They lay eggs in October through December, and the eggs hatch around January. During the mating season, due to their monogamous nature, Rayaditos are very pair-territorial and typically cannot be found without their partner. During the off months of roughly March through September, Rayaditos are extremely social and are known to be seen in flocks of four or more birds.
Because the Rayadito is endemic to Southern Patagonia and is exclusively an insectivore, resource competition with other insectivores exists. Predators of the Rayadito include larger birds, such as hawks or owls, and a few marsupials. The conservation status of this bird is marked as least concern. However, like so many of the endemic species of Patagonia, habitat loss and fragmentation due to anthropogenic causes such as agricultural expansion is always a concern. It’s important to keep this in mind when making conservation decisions, because these little guys need a home- just look at how cute they are (Figure 3)!
