Morphs of the Eastern Screech-Owl
Red morph Eastern
Screech-Owl at Point Pelee National Park on 11 May 2013
Revised January 2014. First
published in Ontario Birds 13(2): 66-71, 1995.
Eastern Screech-Owl (Otus
is a widespread resident in southern Ontario south of the
Canadian Shield (James 1991). It prefers
small deciduous or mixed woodlots with mature trees and snags for roosting
and nesting. The Eastern Screech-Owl is strictly nocturnal.
During the day it usually perches close to the
trunk of a thick evergreen or roosts in a natural cavity or old flicker
rarely more than 10 metres up. On winter days it often sits in the entrance of a south-facing
hole, absorbing the warm sunlight.
disturbed, it retreats down the hole. Many birders are familiar
with its two common calls: a short horse-like whinny in the fall and winter,
and a toad-like trilling in the spring and nesting season.
field guides illustrate and describe two colour morphs,
gray and red, of the Eastern Screech-Owl. Both
the gray and red morphs are illustrated in the National Geographic
Guide (Dunn and Alderfer 2011), and the Peterson Field Guide (2008). In addition,
there is a little-known brown or intermediate morph.
In this account I discuss the identification, frequency, genetics,
and some ecological differences of the three morphs of the Eastern
Screech-Owl in Ontario. The three morphs are illustrated in Voous (1988),
Sibley Guide to Birds (2000)
and by Peter Burke in Figure 1.
Godfrey (1986) and James
(1991) list O.a. naevius
as the only subspecies of the Eastern
A much paler subspecies
breeds in western
intergrading with eastern naevius
at Winnipeg and Whitemouth. These locations are shown on the map on the inside cover
(Godfrey 1986). Other
subspecies in North America
listed in the American Ornithologists' Union Check-list
treatment of subspecies is in need of revision. I agree with DeBenedictis (1977) that
the most sensible treatment of subspecies is by Marshall (1967) who
lists five subspecies:
nominate O.a. asio
(includes naevius of the AOU 1957 and Godfrey 1986) of the
of the AOU 1957 and Godfrey 1986) of the Great Plains, O.a.
of Florida west to
of Texas, and O.a.
of the Rio Grande Valley. The Eastern Screech-Owl account in The
Birds of North America On-line (1995) has a map of the distribution
of the currently recognized subspecies.
Morphs vary in hue depending on whether the subspecies is dark or
pale. For example, compare the eastern gray morph with the paler
western gray morph maxwelliae (includes swenki) on
page 287of the National Geographic Guide (Dunn and Alderfer 2011).
the red morph of the western maxwelliae is paler than the
eastern red morph.
the three morphs of the Eastern Screech-Owl not considered
Subspecies are forms having separate breeding
interbreeding where their ranges meet. Morphs are forms occurring in the same breeding range,
with different morphs even occurring in the same brood.
The third part of the scientific name is the name of the subspecies,
is the subspecies in Ontario (AOU 1957). It has three morphs.
Morphs do not have scientific names. In screech-owls,
the morphs are more recognizable than the subspecies.
1. Three morphs of the Eastern Screech-Owl by Peter Burke published in Ontario Birds
Vol.13 No. 2,
Plumages, Molts, Aging and Sexing
The sexes are similar in all
ages and plumages. Juveniles (juvenals) in summer are narrowly barred all over,
except on the wings and tail which are much like the adult.
Gray and red morph juveniles usually are distinguishable in the field.
See the illustration of the gray morph juvenile on page
287of the National Geographic Guide (Dunn and Alderfer 2011). In late
summer and early fall,
juveniles undergo a partial molt to first year (first basic) plumage,
retaining the juvenile wings, scapulars and tail. First
year birds and adults (definitive basic) are similar in appearance.
First year birds (when they are one year old) and adults undergo a
molt from late July to mid-November to fresh adult plumage.
Colours become faded and dull on worn birds by the next spring and
See Bent (1938) for excellent descriptions of plumages and molts in
first year birds and adults. Partial and total albinos are known in this species
(Holt et al.
Figure 2. Data from
Table 1 in Owen (1963)
three morphs vary in colour and in the extent and pattern of
feathers. See Figure 1. Out of a total of 1320 specimens
(1963) from throughout the range,
were gray, 38 percent red and 8 percent intermediate (brown). In his
study, Owen divided 833 screech-owls from selected areas into six
colour types, grading from gray to red: two gray, two intermediate
(brown), and two red. Figure 2 shows the strong bimodal (gray and
red) distribution of the morphs and the continuous variation between
the morphs. The gray, brown and red morphs are not linked to age,
sex or subspecies. A bird is hatched a certain morph and remains
that colour all its life. All three morphs have been observed in the
same brood (Hrubant 1955,
There are two main theories for the three
the gray and red morphs are due to one gene having two alleles (forms) with red
dominant over gray, with the brown morph due to other modifying genes;
(2) the morphs are due to one gene having three alleles with a
graded order of dominance, red over brown over gray (Hrubant 1955,
and Henny 1975, DeBenedictis 1977). There is no clear resolution
of which hypothesis is correct. Perhaps
the variation observed in
morphs is under the control of more than one gene.
morph is the most
morph in Ontario and throughout the northern part of the
3. Based on specimens in the
Martin (1950) reported that 81 percent of the population in Ontario
was of the gray morph.
Martin did not recognize a brown morph, apparently lumping gray and
brown birds in his study. Gray morph birds in fresh plumage in fall are a clear gray,
becoming tinged with brown on worn and faded birds in spring and
summer (Kaufman 1990).
brown morphs are a richer cinnamon-brown colour,
including the facial disc.
Figure 3. Gray morph
Eastern Screech-Owl in Toronto, 20 January 2011
morph screech-owls are bright, “a gorgeous rufous like a red fox"
(Marshall 1967). Red morphs comprise
about 19 percent of the Ontario population,
specimens in the Royal
birds are uncommon in the northern parts of the screech-owl's range.
Why? The reason may be that red morph birds have a lower survival
rate than gray birds during unusually cold and severe
winters. Plumage colour is correlated with thermal adaptation.
Mosher and Henny (1976) found under laboratory conditions at -5°
C and -10°
C that red
higher metabolic requirements than gray birds.
Differential mortality was observed in an Ohio study by VanCamp and
Henny (1975). They report that 44 percent more red birds died than
gray birds during the particularly
severe winter of 1951-1952. Perhaps the
percentage of red
birds declined in southern Ontario
during the winter
one of the snowiest and coldest
winters on record! Similarly, Gullion and Marshall (1968) in Minnesota
found a differential mortality between red and gray morph Ruffed Grouse (Bonasa
to winter survival. Why red coloration is linked to winter
in these two species is unknown.
are two additional differences between gray and
birds that are noteworthy. First, Kay McKeever (pers. comm.) reports that "the feathering on the legs of red birds appears to be less
on grays". Second, red birds spend more time in cavities
winter days, 80 percent (red) versus
38 percent (gray) (Voous 1988). Bruce Di Labio (pers. comm.) reported that the red bird of a mixed
observed for many years in Ottawa often was more difficult to
in winter than the gray bird.
Figure 4. Red morph
Eastern Screech Owl at Burlington, 27 Feb. 2012
or intermediate morph is by far
least common form in screech-owl populations,
where intermediates make up to 40 percent of the
from Ontario admitted to The Owl Foundation in Vineland,
percent were classified as brown morphs by Kay
New York specimens in eight state museums; only four or 2.78 percent
were brown morph birds.
(pers. comm.) and Tim Dyson
banded an intermediate morph screech-owl on 4 March 1995 near
Peter described it as “very beautiful indeed. The overall coloration was dry gray-brown,
of bright rufous-reddish areas on the scapulars and
Kay McKeever (pers. comm.) of The Owl Foundation
in Vineland describes the brown morph as a "warm brown like a saw-whet
Ross James (in litt.) of
the Royal Ontario Museum says "there is considerable variation in
the brown coloration depending on whether it tends towards
or grayish. In general, the brown is more of a cinnamon
or tawny brown as opposed to a dark chocolate, reflecting a mix of reddish tones on one side
and lighter or whiter gray on the other".
England the brown morph is described as being
chocolate brown in colour (Smith 1993), but intermediate birds from
Ontario in the ROM are not chocolate brown (Ross James,
pers. comm.). Similarly, Kay McKeever (pers.
has never seen a chocolate brown Eastern Screech-Owl.
aware that brown
morph screech-owls could be overlooked as
gray birds given
a frontal (ventral) view. The rich brown coloration is most apparent on the upperparts
(dorsum), the side least often
identifying a brown morph, keep in mind that recently molted
in fall in fresh plumage are clear gray above, but become tinged with brown on worn
and faded birds by
and summer (Kaufman 1990).
Figure 5. Brown morph
Eastern Screech-Owl in Toronto on 1 March 2008
and red morphs. The gray morph is the most common, comprising about
80 percent of the Ontario
morph is less than 20 percent;
and the brown morph is the rarest, comprising less than three percent. Typical
(most) individuals of each morph are easily
variation between red and gray birds.
advice and assistance
in the preparation of this article, I thank Peter Burke,
Bruce Di Labio, Tim Dyson,
Godfrey, Michel Gosselin, Mary Ellen Hebb, Jean Iron, Alvaro
James, Kay McKeever, Dwight Smith, Ron Tozer
illustration of the three morphs is a masterpiece that greatly enhances the
Figure 6. Front cover of
Ontario Birds Vol.13 No. 2. 1995. Illustration by Christine
Ornithologists' Union. 1957.
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Dunn, J.L. and J. Alderfer.
2011. 6th Edition. Field Guide to the Birds of North America.
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asio), The Birds of North America
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Retrieved from the Birds of North America Online:
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Lichen Place, Toronto ON M3A 1X3.