Saturday, June 13, 2015

Mantanani Scops Owl: Conserving A Supertramp

The Mantanani Scops Owl (Otus mantananensis) is a fascinating small island specialist that is considered globally Near-threatened.  The Mantanani Scops Owl has a very small global range, being found only on several very small islands off the coast of Borneo and in the Philippine Archipelago but absent from larger islands (the name derives from Mantanani Island).

Island endemism is very common in some small owls such as Otus and Ninox. Some islands may even support more than one endemic owl species. Both of these genera have some dispersal capabilities over water, including migratory species wintering on islands. In fact, small flocks of Northern Boobooks have been observed migrating over the ocean off the coast of South Korea. The ancestors of today’s island endemic owl species presumably would have dispersed over water (although probably aided by land bridges in many cases) and evolved to be capable of speciation on small islands and subsequent maintenance of self-sustaining populations on those islands, even when the islands were very small. Species that are adept at over-water colonisation of small, species-poor islands (but which tend to be excluded from larger species-rich islands) are often referred to as “supertramps”. This term was coined by ornithologist Jared Diamond in 1974 (now famous for his books on human history such as "Guns, Germs and Steel"). In the case of the Mantanani Scops Owl, it is not clear whether tiny populations persist on tiny islands or whether there is movement between islands (colonisation and recolonisation) so this species perhaps doesn’t quite fit the classic definition of a supertramp, even though it has some supertramp characteristics.

The supertramp lifestyle (or variation of it), in part because of the lack of stability that is inherent in the name, poses challenges for conservation. For one thing, conserving these species requires maintaining or permitting the successional processes that make island chains so dynamic, i.e. there has to be enough habitat on different islands to allow the supertramps to colonise new areas when the island/site they occupy either becomes more mature or suffers fresh natural disturbance. The habitat on tiny islands can be in a state of flux due to disturbance from extreme weather events. The supertramp strategy can cope with tsunamis, hurricanes, monsoons and gales but if we as conservationists want to conserve that rich dynamic, it means that we cannot simply conserve island X to save species Y. We need a big picture approach that allows for a full suite of ecosystem processes, habitats that change both naturally and from human intervention, and species whose abode is not quite “fixed”. Well, surprise, surprise, it turns out that we need big picture approaches not just for small islands but really for all conservation. It also turns out that human beings really prize stability and don’t seem to cope well with change. We don’t like moving our towns and cities any more than we like moving our national parks, even when that would be the adaptive thing to do. In reality, the supertramps could teach us a thing or two about one of Mother Nature’s great ironies: change = stability and stability = change!

For the Mantanani Scops Owl, things don’t look all that rosy at the moment. The habitat available to them is limited and although this could change for the better, it also could change for the worse! For example, human population pressure on the Philippines, which forms most of the species’ range, is rapidly reaching crisis level (already over 100 million people in just 300,000 km2 and growing all the time). With increasing human pressure on these little islands and their limited resources, any small amount of habitat loss can have a big impact. There is very real concern that some of these islands populations will be wiped out. That has almost certainly happened over the course of the evolutionary history of this species but the problem will become critical if there aren’t enough new areas to colonise to ensure the species’ long-term survival. The problem will come if we don’t plan for change!

With increasing human population pressure and with rising ocean levels, the future is very uncertain for small oceanic islands and the rich biodiversity they are home to. We simply cannot afford to watch and wait for the loss of this richness. We should plan for the future by learning from these species that have survived for so many thousands of years in such harsh and changing environments. Although I see it as very challenging, I do believe that we can still find ways to conserve island endemic species and supertramp species.

Here are 7 photos to introduce you to this species. The first four are of the nominate subspecies on Pandan island, a tiny island off Palawan, Philippines. The next three are of the romblonensis subspecies on the island of Tablas, Philippines.  

This first photo gives you a sense of the small size of this owl.
 This next photo shows the nictitating membrane closing to protect the eye.You can also see a little of teh wing droop posture often used when singing or in territorial disputes.
 This is the calling posture (note the inflated throat).
 And finally, a portrait!

These next three photos show the romblonis subspecies from the island of  Tablas, Philippines. This subspecies is more coarsely marked on the underparts than the nominate. 

This photo again gives you a sense of the size of this owl.

Finally, this flight shot shows the underparts and a little glimpse into night world of this fascinating species.

There are two other subspecies not shown here as well. 

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