A few owls of South Korea

A recent visit to South Korea was not primarily a birding trip but will a little help from some old friends I managed to find a few of South Korea’s wonderful owls that I have wanted to see for many years.

First and foremost on that list was this Ural Owl (Strix uralensis) in the mountains of the northeast, who offered a splendid viewing opportunity shortly after dusk.  These large, pale owls are widespread across the taiga / boreal portions of Eurasia are somewhat of an ecological equivalent of Barred Owl in North America.  With the largest females measuring 62 cm and weighing as much as 1.3 kg, Ural Owl is one of the largest species is the genus Strix (Great Gray Owl is larger but Ural Owl is approximately 10 cm longer than Barred Owl.  The Korean subspecies is S. u. nikolskii.

Similar to the Ural Owl but much smaller in size and darker in colour is the Himalayan Owl (Strix nivicolum). This species is also known as the Himalayan Wood-Owl or the Chinese Tawny Owl, although none of these names are apt (the distribution is not restricted to the Himalayas nor China). I was delighted to find this roosting bird tucked in against a tree trunk and definitely aware of my presence probably well before I spotted them. This species used to be considered conspecific with Tawny Owl (Strix aluco) from Europe and westernmost Asia but their song is quite different and the Himalayan Owl is generally darker with a shorter and more barred tail and a second “wing bar” usually visible.  This bird is a grey-brown morph, although there is apparently also a rufous morph, which I have never seen. You will see how the owl's plumage works so well as camouflage against the tree bark. The Korean subspecies is S. n. ma.

  

Finding a nest of Japanese Scops-Owl (Otus semitorques) was a major highlight. They were super secretive around their nest but I managed a few photos including one where a small mammal prey item was brought in. I was surprised to observe a pair of Siberian Flying Squirrels (Pteromys volans) that seemed to be using a cavity lower in the same tree (third photo). Interestingly, this northern scops-owl species is apparently resident in South Korea, unlike some other northern scops-owls such as Oriental Scops-Owl that are migratory. Nonetheless, there may be some altitudinal or short-distance migratory movements of this species in other parts of their range. Famous for their red eyes, unlike most other members of their genus, this species was once considered conspecific with “Collared Scops-Owl” which has now been divided into at least 4 species (they differ in voice, wing formula and some subtle plumage details).  The Korean subspecies is the nominate. 

 

I also saw two Eurasian Eagle-Owls in South Korea but it was raining and a few poor flight shots were all I managed such as the one below.

I hope you enjoyed this glimpse at the owls of South Korea!

Great Canadian Birdathon

American Woodcocks will be back very soon and "spring" shortly behind them! This spring can you help us raise funds for bird conservation with the Great Canadian Birdathon either by becoming a member of the atlas birdathon team or by supporting one of the team members. See:  http://birdscanada.kintera.org/faf/search/searchTeamPart.asp?ievent=1129177&lis=0&kntae1129177=7AD9B5FE4684468FB0FDDBDC92EC9C49&team=6319959 

On the Mobbing of Owls

The photos in this blog post show six owl species from five genera being mobbed by potential prey species. Although only one individual of each prey species is visible in the photo, other individuals were present during the mobbings and sometimes multiple species were present. Mobbing is when prey species, usually in groups, harass a predator using loud calls and possibly also stereotypic movement sequences (that can recruit other birds to join the mobbing party). Note that mobbing is an interaction between predator and prey and is different to a competitive interaction as may occur between an owl species and a hawk species for example. Mobbing sometimes succeeds in driving a predator away from an area, which is an obvious benefit, but it also comes with risks. These risks may be higher when mobbing certain predators. Mobbing nocturnal owl species during the daytime is probably less risky than mobbing diurnal raptors and is sometimes successful in driving the owl away from a roost site; however birds that mob owls are sometimes killed by the owl they are mobbing. Although many owls seem disturbed by mobbing, some owls might benefit. One of the several competing hypotheses as to why certain species have large “false face” markings on the back of their head is to evoke a mobbing response that subsequently provides either a prey assessment opportunity or a hunting opportunity. Mobbing is not restricted to owls of course, nor is it restricted to nocturnal owl species (one of the photos above shows a day-active Northern Hawk Owl being mobbed). Sometimes recently fledged juvenile owls get mobbed and if they are knocked from their perch during the mobbing the result can be fatal (the owlets are vulnerable on the ground).

In the case of owls, the loud mobbing calls of diurnal songbirds are often the first clue for the human observer that a nocturnal owl is roosting nearby. Therefore, if you learn to recognise the mobbing calls of bird species that are common in your area you will increase your chances of locating owls.

We really don’t know why small birds mob owls but there are many hypotheses to consider. Curio (1978) listed nine hypotheses as follows: silencing-offspring, selfish herd, confusion effect, move on, perception advertisement, alerting others, attract the mightier, cultural transmission and site avoidance. These have been grouped into three main “classes” of hypothesis: parental care, altruistic or selfish (Ostreiher 2003). At this point, we don’t have enough evidence to evaluate which of these hypotheses is correct and therefore detailed observations of mobbing behaviour are especially useful. Especially in situations where you can distinguish the age or sex of prey birds, your observations may be informative. In the very rare situation where the observer understands the kinship amongst mobbers, there is also potential for garnering new information (kin selection is a possible mechanism to consider in behaviour of this type).  

Eastern Screech-Owl (Megascops asio) being mobbed by Blue Jay (Manitoba, Canada)

The crow family are some of the most frequent and most ardent mobbers of owls and they are capable of causing an owl to flee. This male Eastern Screech-Owl retreated into his roosting cavity when mobbed by Blue Jays (the female and large nestlings remained ensconced in the nesting cavity nearby).

Great Horned Owl (Bubo virginianus) being mobbed by American Crow (Manitoba, Canada)

Another example of a crow family mobbing owls. Crows are aggressive but tangling with a Great Horned Owl is risky business (I once observed a Great Horned Owl that was apparently fleeing from a flock of mobbing crows perform a near barrel-roll manoeuvre and grab a crow in flight, then killing and eating the crow on the ground).

Northern Hawk Owl (Surnia ulula) being mobbed by Gray Jay (Manitoba, Canada)    
Mobbing a day-active owl is also risky business but this nimble Gray Jay got the owl's attention but did not encounter any problems, nor did the Northern Hawk Owl budge from the perch. Although I have seen Gray Jays mobbing Northern Hawk Owls on relatively few occasions, I have never seen them mob Great Gray Owls and I suspect that may be because Great Gray Owls are so specialised in the prey selection that they almost never take birds.

Pearl-spotted Owlet (Glaucidium perlatum) being mobbed buy Senegal Eremomela, Cameroon

Mobbing a day-active Glaucidium species (pygmy-owls) is probably the most risky of all. These tiny owls are lethal predators and they strike with surprising speed. Some authors have hypothesised that the false-face on the back of the head of some pygmy-owls incites mobbing and that the owls use this to their advantage.

Peruvian Pygmy-Owl (Glaucidium peruanum) being mobbed by Amazilia Hummingbird, Peru 
Owls are mobbed by more than just songbirds as this Amazilia Hummingbird demonstrates. This is another case of one of those highly–feared pygmy-owls being mobbed by nervous prey species.

Tengmalm’s Owl, also known as Boreal Owl (Aegolius funereus) being mobbed by Red-breasted Nuthatch (Manitoba, Canada 

In North America, chickadees and nuthatches are amongst the most frequent of mobbers and they seem to understand each other’s alarm calls and readily mob owls together.

Of course, these are only a few examples.

Subtlety and beauty

On a recent visit to the high Andes of Ecuador, I was absolutely delighted to find a truly extraordinary shorebird of the high elevation bogs and alpine tundra, The Rufous-bellied Seedsnipe (Attagis gayi). The seedsnipe are a small family (Thinocoridae) of only four species of rather stocky shorebirds, found only in South America, whose diet is largely vegetarian (seeds and plant material) unlike the majority of shorebirds.

These birds are exquisitely plumaged such that their camouflage is exceptional but when seen well the feather detail is also truly breathtaking. I will try to let the photos speak for themselves. The first photo shows two Rufous-bellied Seedsnipe in their habitat. Can you spot them? If not, take a look at the second photo for help...

If you spotted those birds, congratulations! Now here are two photos with a telephoto lens to show off their exceptional beauty up close and personal. 

I hope you enjoy looking at these photos as much as I enjoyed finding these magnificent birds!