Mountain barriers

Mountains are important engines of evolutionary change. A mountain range can present a formidable barrier to movements of animals and divide populations, preventing them from exchanging genes with one another. The division of a single population into two by the gradual introduction of some geographic barrier, like the uplift of a mountain chain, is known as a vicariant event. Vicariance is an important process in evolutionary change and is responsible for much of the biological diversity we see today.

Taiwan has, by all appearances, an excellent example of a vicariant event dividing a single ancestral population into two separate species. The bulbuls are widespread Old-World family of birds (Pycnonotidae). Taiwan has several members of this avian group including the Chinese Bulbul (Pycnonotus sinensis), a widespread bulbul in East Asia, found both on the island of Taiwan and in Mainland China (see photo left). The Chinese Bulbul's name in Mandarin Chinese is "Bai Tou Wang" which means "white headed old man" after the characteristic white patch on the back of the head. This bird is abundant at low elevations throughout Western and Northern Taiwan where it is considered a crop pest. Farmers often leave fine nets up around their fields that snare these birds in flight and they are left to die hanging tangled in the mesh of the net. A little cruel, yes, but this practice is tolerated largely due to the fact that prohibitions against netting wild birds can be difficult to enforce due to a variety of reasons. Also, the netting occurs in agricultural areas where most of the birds killed in these nets belong to very widespread and common species.

There is also another very similar bulbul is found on Taiwan. This is one of the 16 endemic avian species found on Taiwan, the Taiwan or Styan's Bulbul (Pycnonotus taivanus), found on the east side of the Taiwan Central Mountain Range. This bulbul is very similar to the Chinese Bulbul with a notable exception being the lack of white on the back of the head (see photo right). Because these two species occur on either side of the Taiwan Central Mountain Range they appear to be a classic example of speciation due to a vicariant event, in this case the uplift of Central Taiwan. Different species divided by mountain ranges, bodies of water or other geographic features is a common occurrence among birds and in Taiwan we can see this on a relatively small scale.

However, the two species do have a zone of contact in Southern Taiwan where their ranges overlap and they hybridize so their genetic isolation is incomplete. Taiwan and Chinese Bulbul seem to be a case of vicariance in action but recent work suggests that despite their differing appearance there are few genetic differences between these species. These birds are great subjects for future research and genetic comparisons of these species can potentially tell us much about how new species form.

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The Hilton it ain't...

Watching the Discovery Channel you may think of field biologists in far flung corners of the globe tracking down rare plants and animals in exotic locations. Not all field biology takes place in exotic, "wild" locales. Often the subjects of one's research are pretty ordinary suburban organisms like Grey Squirrels (Sciurus carolinensis) or House Sparrows (Passer domesticus), but, sometimes research does take you far afield into more adventurous settings.

But, what is often left out is just how dirty and difficult field work can be. This weekend's field expedition across Taiwan's south cross highway to the east side of the Taiwan Central Mountain Range was about as unglamorous as field work gets. We managed to find a tea plantation that allowed us to stay in the workers quarters on the cheap (see photo left). Normally during the height of the tea harvest there are 50 plus workers staying in this modest building. Luckily save for the farm manager and a couple workers we were the only people staying on the farm. The sleeping area consisted of a concrete floor and a raised platform where we all slept on moldy comforters. The kitchen doubled as a storage room/office and we ate instant noodles lunch and dinner with some pork or boiled cabbage on the side and bread for breakfast. I'll leave the bathroom undescribed to spare the reader the more graphic unpleasantries of fieldwork.

However, life aways has trade offs and spartan living conditions are balanced by seeing some great birds, getting some good data and enjoying some spectacular scenery (see me in photo right). Somehow the birds, the scenery and the camaraderie of one's colleagues stick in my mind a little more than the living conditions and this keeps me coming back to the beautiful mountains of Taiwan. Sleeping on hard surface or eating a steady diet of cabbage and instant noodles are sometimes worth it to see these fantastic views and incredible wildlife.

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Another shrike!

This trip seems to be the year of the shrike. In addition to the common species found on Taiwan during this time of year, the Brown Shrike (Lanius cristatus) and the Long-tailed Shrike (Lanius schach), we found another member of the Lanius clan. The Bull-headed Shrike (Lanius bucephalus, see photo left) is a rare vagrant to the island of Taiwan. They are more commonly found wintering in mainland China after their breeding season in Manchuria, the Korean Peninsula and Japan. This was a lucky find. We ran across this lone male Bull-headed Shrike while surveying birds on the east side of the Taiwan Central Mountain Range on a tea plantation at about 4,900 feet elevation. These birding surveys are important as they document the movements and distribution of birds during different times of the year. Knowing about bird distributions and movements are critical in understanding different ecological and evolutionary processes in avian species and long term data can potentially tell us about the ecological effects of global climate change. Maybe Bull-headed Shrikes will be a more common sight in the future? Maybe not? We'll need lots of keen eyed birders to keep watch for these and other rare vagrants.

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Shrikes, killer songbirds

Most songbirds we encounter are mild-mannered little birds that eat seeds or small insects. Members of the shrike family (Laniidae) are exceptions to that rule. Shrikes prefer open habitat where they survey their surroundings from a high perch for passing prey items. Top of the menu are large insects, like grasshoppers, and often other vertebrates like lizards, mice or small birds. To kill vertebrate prey shrikes have a special adaptation, the tomial tooth, an extension of the upper mandible that shrikes use to dislocate the neck vertebrae of their prey. Falcons have evolved a very similar structure independently of shrikes and use it in much the same way to dispatch their prey. Shrikes are also famous for keeping larders of their prey for later. A shrike's larder consists of large insects and vertebrate prey impaled on thorny bushes and trees or in some areas on barbed wire fences.

We've seen many shrikes during this latest trip to Taiwan with two species making up all the sightings, the Brown Shrike (Lanius cristatus, see photo above taken at the Aogou wetlands on Dec 10) and the Long-tailed Shrike (Lanius schach, see photo right taken near Yuanshan on Dec 8). There are only two species of shrike in all the Americas and neither of American species are found on the island of Taiwan. Eurasia and Africa are the strongholds for shrike diversity with most of of the 28 species in the genus Lanius occurring on these continents. Brown Shrikes are winter migrants but Long-tailed Shrikes can be seen all year on Taiwan. Lanius shrikes are common but still great birds to see on any trip to Taiwan.

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The crane! The crane!

Cranes are popular birds in the far east with an important place in Chinese, Korean and Japanese art and culture as symbols of peace and harmony, so when they show up unexpectedly in places where they aren't normally seen it can be a big deal. On December 7 during this year's trip to Taiwan, with University of Minnesota student Bailey McKay, we had the good fortune of seeing four wintering Red-crowned Cranes (Grus japonensis) in the agricultural fields around Jingshan. The sighting was easily made from the roadside with binoculars and a spotting scope gave excellent looks at this beautiful bird. A single adult plumage individual was in a grassy field along a river filled with Black-crowned Night Herons (Nycticorax nycticorax) and other waders. A short drive around the corner from this bird revealed three more individuals (2 in adult plumage and 1 in juvenile plumage, see photo left. I know it isn't the greatest photo but the birds were very far away.). This was a big surprise as it was only the third record for Red-crowned Crane in Taiwan and the first such sighting in four years. Prior to the last sighting four years ago there were no records of this species for over 60 years! All previous sightings were of solitary individuals making this year's sighting the largest known wintering population of Red-crowned Cranes in Taiwan to date.

Local birders were already on the scene when we arrived at this site. In Taiwan birding is a major pass time and a half a dozen birders with 2,000 dollar spotting scopes and a 600 mm lenses on a 10 mega pixel digital camera is not an unusual occurrence, particularly in the winter when there are many different vagrant and transient migratory birds. Typically the first person to spot a rare bird are on their cell phones and within the hour birders from around the island are packing their gear and on the way. Our presence at the crane site attracted a lot of attention even by non-birders and soon after our arrival a line of locals had formed waiting to catch a glimpse of the cranes through Bailey's spotting scope (see right photo). One never knows what will turn up in the winter in Taiwan! Taiwan is a great place for these rare vagrant migrants and a great place to meet many enthusiastic, friendly birders.

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