Friday, June 15, 2012

Dastardly Duos - Pygmy-Owls

By Larry Liese
From the Vermilion Vaults
Originally appeared: May/June 2003 issue

Everybody likes owls. I don’t know anyone who won’t drop his or her binoculars (not literally) from viewing a ‘regular’ bird when someone spies a day-roosting owl and calls out “I’ve got an owl here!”

This issue’s duo is two cute little owls belonging to a family of owls characterized by diurnal behavior, long tails and ferocious aggressiveness. They’ve got attitude! Often taking prey their own size or even larger, pygmy-owls are not known as ‘cute’ to the songbirds of the world, and are frequently mobbed by them when found. An imitation of their whistled calls will frequently bring in a host of small birds, all wishing to shoo the owl out of their area (please see note at end of article).

An uncommon permanent resident in our area, the Northern Pygmy-Owl (Glaucidium gnoma) is found in open coniferous and mixed woods above 4000 feet elevation. Two subspecies are present here, G. g. pinicola, which gives single hoots and is thought to reach its southern limit in the Catalinas, and G. g. gnoma, which gives double hoots and is found in the mountains south of the Catalinas down through Chiapas, Mexico. (More on hoots below.) Very rare and local in our area, in dry riparian habitats at low elevation is the similar appearing Ferruginous Pygmy-Owl (Glaucidium brasilianum). Source of much controversy with regards to habitat protection and the Endangered Species Act (ESA) in our area, this formerly common species has dwindled to a few tens of known individuals north of the border. The subspecies here is the Cactus Ferruginous Pygmy-Owl, G. b. cactorum, different from the one in southern Texas.

Both of these owls are often heard from a distance. The whistled hoots of the FPO are a rapid whi-whi-whi-whi- ... typically three per second with rising inflection, continuing for what seems like minutes, the Energizer Bunny of the owl world! The pinicola form of NPO gives a slower single hoot than the Ferruginous, but much faster than NPOs from northern states; roughly one to two per second. It is a clear whistle of more constant pitch. The gnoma, or ‘Mountain’ Pygmy-Owl form breaks into a double-hoot, with odd single hoots thrown in, but clearly double for the most part. The double hoots are given about a second apart and have a similar tonal quality to the pinicola form. Don’t be surprised if this species is split in the future.

Since these two owls are not found in the same habitat, you shouldn’t have trouble discerning which one you’ve run into, but here are the visual characteristics that distinguish them. NPOs have a dark brown head with many small white spots on the crown, have coarse dark streaks on white underparts, white spots on their brown sides, and have a long tail with alternating white (narrow) and dark brown (wider) bands. The brown colors of FPOs are lighter, they have fine white streaks on their crowns, unspotted sides, similarly streaked white underparts, a slightly longer tail with alternating brown and rufous bands (no white). Their tails have more bands than the NPO, but they would be hard to count in the field!

Interestingly, these owls lack the feather adaptations of the nocturnal owls – the soft comblike leading edge and fuzzy upper surfaces that quiet their approach. They have dark ‘eye-spots’ on their napes thought to confuse mobbing birds and increase predatory efficiency by confusing prey. They have large territories, up to a mile in length. They attack in a rapid pursuit flight. Large prey items for these two have included American Robin (NPO), and Gambel’s Quail (FPO). Ferocious indeed!

So, if you’re out birding, particularly at dawn or dusk, and hear some whistled hoots, you may be in for a treat – but don’t drop your binoculars. Good luck!

NOTE: As birding has become more popular, activities such as pishing, whistling imitations and playing recordings of bird songs and calls to attract them have come under debate as to their impact on the birds we are trying to enjoy. If you are one to go out and enjoy what nature offers you without these enhancements – more power to you! I’m told that performing any activities such as these is ILLEGAL for animals protected under the ESA, which holds for the Ferruginous Pygmy-Owls here in Arizona

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