The Variable Brown Shrike

posted in: Morphology-Develop., Species | 0

“I find that with Brown Shrikes (Lanius cristatus), the more I watch the less I know. My wife, a keen bird watcher, says that Browns Shrikes are confusing to her and that many look different. I went out today to try and document Brown Shrikes in my urban neighbourhood. I choose this location as it is an old mature housing area where many homes have open gardens and trees which support the habitat of Brown Shrikes.

Post 1. Brown Shrike (details see below).

“I watched for 2.5 hours using the car as hide. The area I covered was 655,000 meter square (65.5 hectare, calculated using Google map) which is basically 3 housing estates. I revisited the same locations at least 3 times each to try and ‘saturate’ my observations. I did this knowing that migratory Brown Shrikes defend their wintering territory. I have often seen the presumed same bird return to the same patch in our neighbourhood. Wells 2007, commenting on this says “Winterers defend exclusively feeding territories, small (typically less than one ha)…”

Post 2. Brown Shrike (details see below).

“I identified at least 17 different birds and may have missed some. There will be concerns that my observations overlap birds (i.e. same bird counted as a different bird) and I admit it is possible. But note the discussion above about small wintering territories. I also manged to image 13 out of the 17 birds which allowed for individual characteristic to be differentiated, so the minimum in that area would be 13. Note that at two locations, I saw birds only 5 meters apart with no aggression. On one occasion it was adjacent to a field which allowed for a larger feeding area.

Post 3. Brown Shrike (details see below).

“Eshkab I.A. did a local survey on ‘Population of Brown Shrike (Lanius Cristatus) in Grassland of University Putra Malaysia’ in 1999 (PDF) and reported a density estimate of Brown Shrike in the range of 0.35-0.81 birds per hectare. My observation (assuming 17 birds) would mean 0.26 birds per hectare. But I estimate that I could have missed about 30% of birds this morning. My habitat is also more built up from his.

Post 4. Brown Shrike (details see below).

“Of the 17 birds seen only 3 were adult males, 7 females and 7 first year, immature birds (I am avoiding the term “first winter” as it can be confusing in the literature). I am also avoiding subspecies discussion here and focusing on the characteristics for sex and age; using mainly feature in the head and upper part of the body. Note that males were the hardest to image and the most likely to react negatively to the camera.

“Post 1 shows a face composite of 4 adults. Bird 1 is an adult male. Bird 2-4 are presumed adult females with varying degrees of barring on the body (least barring with Bird 2, most with Bird 4):
1. The Bill – in adults expected to be black/bluish; but in all adults I saw there was pink at the base and on proximal lower mandibles.
2. Ear coverts –expected to be black in adults; note Birds 2 and 4 have brown ear coverts.
3. Lores – in adults usually well developed & dark black; note belter developed in Birds 1 & 3.
4. Supercilium – note Bird 4 where it is poorly developed or minimal.
5. Underpart Barring – females have variable amounts of vermiculations.

“Post 2 are full images of Bird 2, 3 and 4.”

My questions:
1. When does underpart barring disappear in adults? At the end of the first year of life or later? If it can persist than perhaps Bird 3 is a second year male?

2. Is my identification of age for Bird 4 wrong and is it a first year/immature bird rather than a adult female? But I saw other heavily barred adult females with good lores and black eye coverts. Also I saw the bird well, with many images, and it did not fit well as an immature bird. Again if barring persists into the second year could this be a second year female?

“Welcome any opinions on the joys of identifying polymorphic (pleomorphic?) Lanius cristatus.”

Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
12th October 2018

Location: Ipoh, Perak, Malaysia
Habitat: Urban Gardens

Reference
Wells, D.R., 2007. The birds of the Thai-Malay Peninsular. Vol. II, Passerines. Christopher Helm, London. 800 pp.

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