Snowy Owls 2017

(Click on images for larger, hi-res versions)
Arriving back from Mexico, it was evident there was an incursion of Snowy Owls Into CT. A widespread arrival across the Mid West had hinted at an irruption year and several birds were found at Long Beach in Stratford – a typical “go to” spot for this species.
Alex and I took a ride down and immediately found a bird sat on one of the closest jetties giving great looks in the scope and decent photo opps. (A dark, female- type bird had accompanied this bird but had been flushed twice by a woman with a point and shoot camera. Grrrr!)
A week later, with continued reports of multiple individuals, I made a predawn assault and obtained some decent shots of both individuals. The birds attracted a lot of attention!
 
Studies by Josephson (1980) and others (see below) have outlined the difficulties in ageing and sexing Snowy Owls. Birds after their first year are in first Adult plumage.  According to studies of known returning birds, it may take four-five years for an adult to reach a definitive basic plumage.
Ageing and sexing Snowy Owls is clearly difficult. In December, First-year (first-basic) males and adult females can overlap in plumage but first-year (first-basic) females are often the darkest and adult males the lightest. However, while that simplistic general wisdom may hold for many birds, some known-aged females never got darker with age, while some known-aged females became as white as older adult males –  clearly field sexing will lead to some mistakes!
Even I had published a note on ageing and sexing them based on a bird seen in Lincolnshire, UK in 1991 (Hough, 1992). In hindsight, and with a lot more Snowies under my belt, that note was perhaps a little simplistic in dealing with ageing and sexing…it is way more complicated than I could ever have known at that time.
While many individual birds won’t be able to be confidently aged and sexed in the field, studies done on the breeding grounds (Seidensticker et. al) and of museum skins hint at certain helpful criteria to focus on:
  • vermiculations on the scapulars, primary tips, and inner greater coverts.
  • barring on the nape
  • presence of barring or spotting on the inner secondaries
  • number of tail bars
  • any molt contrast in the primaries
  • density of barring on the upperparts and crissum
While it is clear that field views may not provide accurate clues to age and sex, some birds can present with enough features that a good guesstimate of age and sex can be attempted.
First-basic birds sport primaries and secondaries of the same generation and have relatively pointed primaries. Tail is similar, though many of these young birds can show growth bars that while visible in the hand, are not visible under normal field conditions. Males generally show spot-like markings on the secondaries that do not touch the rachi, while females tend to show more bar-like markings, often broader and blacker. Males show 2-3 broken tail bars while females typically average more, usually 3-6.

Apparent first-basic male Snowy Owl, Stratford, CT, Dec 2017

Apparent first-basic male Snowy Owl, Stratford, CT, Dec 2017 (same bird as above). a) Pointed primaries with slight mottling; b) three tail bars; c)brownish mottling on tertials and spot -like markings on secondaries.

To summarize, while the darkest, heavily marked birds are likely to be first-basic females, first-basic males can be variable, being dark first-years or light first-year birds. These birds typically have mottling in the scapulars, tertials, greater coverts, and between the bars on the primaries, that will help separate them from adults.
However, some first-year birds may show reduced mottling – a lack of such markings may not indicate that the bird is necessarily an adult.

Apparent first-basic male Snowy Owl, Stratford, CT, Dec 2017 (same bird as above). A rather pale bird, with unmarked nape, narrow barring on underparts, rather extensive white bib (compared to female). Mottling on rearmost scapulars, tertials and primaries suggest a first-basic bird.

I’ve included a few pictures of the recent birds, and past birds from neighboring states that may be helpful. The captions hone in on certain aspects of plumage that may hint at age and sex, but these are by no means definitive and I welcome comments on anything here that is incorrect. Again, these are just suggestions based on the current literature.
 

Apparent first-basic female Snowy Owl, Stratford, CT, Dec 2017. Larger size, typical of females was apparent in the field. Very heavily barred with reduced white bib, brown mottling on tertials and heavily barred nape. Barring extending onto the vent is also typical of females, especially first-basic individuals.

Apparent first-basic female, Stratford, Dec 2008. Note a)densely barred nape; b)extensive mottling on greater coverts, tertials and some rear scapulars;c) bar-like markings on secondaries; and d) 5 tail bars, with barring extending across both vanes.

Apparent first-basic female, Stratford, Dec 2008. (same bird as above).

First-basic Snowy Owls retain their primaries, tertials and tail until the early summer when they are essentially one year old. By the time we see these birds in Nov/December, they will be second-basic plumage having completed or nearly completed their first primary moult (usually starting with p7). Older birds (e.g.,third-basic) subsequently follow the same molt schedule with p7 being one of the first to be replaced.
So, how do you know in December, if the bird is a first-basic or older? Looking for visible signs of a first-year (see above) and then examining the primaries to see if there is any molt contrast between new, replaced primaries (typically p7) and secondaries. Apparently the differences are subtle, but possible on good close up images of the wing. Also, the newer primary tips often show a more rounded shape with a wider, white terminal fringe.)

Apparent first-basic male Snowy Owl, NY, December 2008. a) Pointed primaries with dark bars reaching to tip; b) spot-like markings on secondaries; and c) three narrow tail bars, Also, shows a noticeable white bib and unmarked vent, further pointers towards a male.

The following references conatin a wealth of information, but as Snowies seemed to be still showing up, hopefully this will help point people in the right direction if they are interested in trying to age/sex birds.

References

Cramp, S. (ed.) 1985. Handbook of the Birds of Europe, the Middle East and North Africa, The Birds of the Western Palearctic, Volume 4 – Terns to Woodpeckers. Oxford University Press.

Hough, J. 1992. Snowy Owl plumages. Birding World 5(3): 96-97.

Josephson, B. 1980. Aging and sexing Snowy Owls. Journal of Field Ornithology 51: 149-160.

McGowan, K.J. 2001. Snowy Owls (Nyctea scandiaca): some recent visitors and thoughts on aging and sexing [online]. Available from: http://www.birds.cornell.edu/crows/snowy.htm [Accessed December 2009].

Pyle, P. 1997. Identification guide to North American birds – part 1. Slate Creek Press, Bolinas CA. 

Sangster, G., Collinson, J.M., Knox, A.G., Parkin, D.T. & Svensson, L. 2004. Taxonomic recommendations for British birds: second report. Ibis 146: 153-157.

Witherby, H.F., Jourdain, F.C.R., Ticehurst, N.F. & Tucker, B.W. 1952. The Handbook of British Birds, Volume 2. H.F. & G. Witherby Ltd., London.

 Mathew T. Seidensticker, Denver W. Holt, Jennifer Detienne, Sandra Talbot, and Kathy Gray. 2011. Sexing Young Snowy Owls. Journal of Raptor Research 45(4):281-289. 2011  https://doi.org/10.3356/JRR-11-02.1

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