Vertical or altitudinal migration

posted in: Migration-Migrants | 4

On 29th December 2006, Susan Wong was birding in Bidor, a marshy area in Perak, Malaysia. As she recalls, “…that day was a super hot day (we got the heat from the ground as well… phew! I mean the sand reflected back the heat to us).

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“As me and my group of photo’s friends took our lunch break under some shade, I could hear the call of a flowerpecker. The very first glance I thought that I saw the Scarlet-backed Flowerpecker (Dicaeum cruentatum) (left)… but oops, my brain maps this species like the one that I saw at Fraser’s Hill at the new road.

“I took a few document shots and went back to refer a few field guides but all seems to says that Fire-Breasted flowerpecker/Buff Bellied Flowerpecker (Dicaeum ignipectus) is the common residents of hill-stations.

I now wonder if it is a new species that we have yet to document ?”

Our bird specialist, R. Subaraj has this to say, “Most interesting and a very nice shot. It definitely looks like a male Fire-breasted Flowerpecker. I do not think a new species is involved.

“So why is a montane species down in the lowlands? There are many movements that are not fully understood or studied and in Malaysia, one such aspect involves a movement known as altitudinal migration.

“Altitudinal migration involves montane species that make movements to lower elevations or even the lowlands during seasonal changes. This normally happens in more temperate countries where the temperature drops significantly at higher elevations, forcing birds to move lower to escape the cold. This migration is well documented in regions further to the north such as the Indian subcontinent. There, many montane species regularly move to the hills or lowlands during the winter period, to return to their lofty homes to breed when spring arrives.

“So why should this happen in the tropics? Well, we certainly do not have the drastic seasonal changes that temperate countries experience. However, we do undergo seasonal changes of a different kind with the monsoon bringing in more rainfall toward the end of the year. As a result, conditions at our Malaysian hill resorts like Frasers Hill and Cameron Highlands are often rainy and misty at the end and beginning of the year. (This can also occur at other times of the year when there is continuous heavy rainfall but is most regular during the north-east monsoon period.) This may force birds to descend to lower elevations. Thus certain species of montane birds are easier to find at lower elevations at particular periods of the year.

“Another reason for local movements is post-breeding dispersal. This happens after the breeding season when adults leave their breeding grounds for whatever reasons (food, seasonal changes, etc.) and fledglings grow up and set forth in search of new territories away from those of their parents. This becomes harder for specialist birds as more and more of their particular habitats disappear each year to development, logging and land clearance for plantations. This may force birds to show up at strange places in desperation or simply by mistake.

“Habitat loss is another reason for birds to be displaced and desperately seek an alternative elsewhere. As the right habitat proves scarce, they may increasingly turn up in the non-traditional habitats, as seen in the 1990s where a large number of lowland species were added to the official Frasers Hill checklist and I was a part of that phenomenon. These birds had never been recorded before in a well-watched site and suddenly there was an increasing number occurring. They were being forced uphill by logging being carried out lower down, along the Kuala Pilah-Raub Road.

“Each year, during the non-breeding period at year’s end or at the start of the new year, montane species may be found in the lowlands, for whatever reason. The most regular is the Mountain Imperial Pigeon (Ducula badia). For years, they have been recorded in lowland sites that have included Kuala Selangor, Kuala Tahan in Taman Negara and even Panti Forest in Johor.

“Even in Singapore, good numbers of Ashy Bulbuls (Hemixos flavala) of the Malay Peninsula race cinereus show up each year between late September/October to March/April. These are supposed to be sedentary birds of the hills. Why would they move to the lowlands and Singapore during the non-breeding season? There have been a variety of other Malaysian forest birds that have been recorded here once or twice over the years.

“So, for whatever the reason, the montane flowerpecker turned up at a lowland marsh and you were there to see and document it. Good record!”

Susan has this to say about her encounter with her vertical migrating flowerpecket: “Looking at both photos, the dull head, messy red chest patch and what appears to be a pale gape, I believe that this bird is not a full adult male yet. This lends support to the possibility of post-breeding dispersal.

“I have heard of butterflies doing short migrations and I am fully aware that birds do migrate for wintering purpose. This is my first encounter of our local resident birds appearing in a different habitat due to some reasons.

“By the way from Bidor to Cameron Higlands, the nearest hill-station, is quite a distance. I estimate it is about two hours car journey to reach the right altitude for Fire-Breasted Flowerpecker.”

Susan Wong & R Subaraj
January 2007

4 Responses

  1. Ding Li | zoothera83@hotmail.com | IP: 137.132.3.6

    I think the subject of altitudinal migration is very interesting and not much studies have been done on it as yet, especially in south east asia. As said, there are indeed a few cases of altitudual migration in peninsular malaysia. Sometimes it may be downwards as seen in dispersal of the mountain imperial pigeon into the lowlands, and likewise the converse can happen. In years of drought, species have been known to move upwards and downwards. Examples include Fruithunter and a few other upper montane species in borneo moving down during extremely dry years (1980s). The opposite happens too. There was a number of lowland birds occuring in higher elevations in fraser’ hill during the dryer than usual periods of 2004-2005. Genuine altitudinal migration is more of a phenomenon of the high mountains, especially the high himalayas, the japanese alps and the rocky mountains, a displacement caused by colder weather. A number of upper montane alpine birds like ibisbill, black-necked Cranes, Hodgson’s Grandala, Snow Pigeon, Red-billed Choughs and many other passerines like thrushes and warblers are known to descend considerable elevations during cold winters. For example, the red-billed choughs in east himalayas which occur normally at elevations of 6000-8000 m descend to as low as 2000 m in winter. I’ve also seen brown dippers himalayan griffons and wallcreepers, birds of upper montane regions coming to as low as 450 metres during winter.

  2. request on the reasos 0n the altitudinal migration in birds.

  3. The reasons are given above: “…So why should this happen in the tropics?…”

  4. Tou Jing Yi

    I tried to check on Google Earth, the closest spot from Bidor wetlands to the nearest forests of at least 900-1000m is just 15 km away, so it is very potential for post-breeding dispersal to happen.

    There was also previously a surprising occurrence of the Chestnut-capped Laughingthrush in a lowland forest edge of a large connected forest in Ipoh, around 10km away from the nearest 900m altitude where it could had occurred regularly.

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