The red warbler, also known as Cardellina rubra, is a tiny bird with an unmistakable bright red color and a lively personality. These little birds vary in size from 12.5 to 13.5 cm in length and weigh between 7.6 and 8.7 grams. As adults, they are entirely red with differing auricular patches on each side of their head, either white or dark grey, depending on the subspecies. The tail and wings have a pinkish-red border and are slightly darker than the rest of its body. The beak is pinkish-gray with a black tip, while the legs are a dull reddish-brown hue. Additionally, the iris color may range from dark brown to black.
The feathers of female birds are usually less bright or have a slight orange tint, but there isn’t a significant difference compared to males. During August, birds undergo a complete moult and adult pairs separate after mating season.
The red warbler is originally from Mexico and can be found in areas ranging from Southern Hidalgo to Southern Chihuahua. They prefer high altitude pine, pine-oak, fir, and oak woods that are humid or semi-humid. Their preferred habitat range is between 2,000 to 3,500 meters.
Warblers prefer to search for food in areas with abundant foliage, particularly in conifer trees, where they can find a diverse range of insects, mainly caterpillars. They use the hover-gleaning technique, similar to that of flycatchers, to catch their prey.
The Warbler with its red face builds a nest that is cup-shaped and situated in a hollow on the ground. Typically, this type of nest can be found at the base of a bush or on a hillside that is open. Sometimes, the nest is located underneath a plant stem, log, or stone which provides shelter and protection for the nest. The female bird creates the nest and lines it with grass or animal hair while utilizing materials including pine needles, bark, or leaves. During the incubation period, which lasts for sixteen days, only the female takes care of the eggs. However, once the young Warblers hatch, both parents work together to feed them. After ten or eleven days, the chicks fledge.
According to the IUCN Red List, the species is classified as Least Concern because it has a vast breeding range and a population estimated to be between 50,000 to 500,000 worldwide. Despite this, their population is dwindling due to ongoing destruction of their natural habitats.