Migratory and Non-Migratory Waders

There are generally two types of research carried out by ornithologist to collect data on birds. They are; i) field research and ii) off-field research.

i) Field research here entails the commonly used methods such as mist netting, tagging, radio telemetry and survey (example observation, interview and questionnaires).

ii) Off-field research on the other hand involves methods such as statistical analysis, phylogenetic studies and literature review (example meta-analysis).

Watching waders via field observation method can be both fascinating and challenging. It can be fascinating due to their spectacular migration pattern as well as their unique behavior adaptation. It can also be challenging due to their amazing variations in seasonal plumage and morphological distinctiveness. Birdlife International defined bird migration as the "regular seasonal movement, often North and South along a flyway between breeding and wintering grounds". These flyways are often described as 'invisible' and many theories have emerged to explain how waders find their way along those flyways i.e from the use of land markings to utilising their own built-in magnetic compass.

Waders can generally be divided into two categories i.e migratory and non-migratory waders. The word wintering and migratory are often used interchangeably and connotes the same meaning. Cambridge dictionary described migratory waders as a bird that travels from one place to another at regular times often over long distance (i.e one that regularly crosses national borders between their wintering and breeding grounds). Boreal migratory waders often breed in temperate countries and winters anywhere from the coastlines of East Asia to Sundaic Southeast Asia and as far as Australia. Non-migratory waders on the other hand are not referring to local endemics but rather migratory waders which for some reasons remain at their wintering ground throughout summer. Perhaps the description by Don Taylor in Helm Field Guides titled "Waders of Europe, Asia and North America" (2014) would best describe the meaning of a non-migratory wader:

"During their first summer, many migrant waders either remain on their Southerly wintering grounds or return only part North. This may explain the occurrence of waders summering in the Southern hemisphere that look like non-breeding adults"

Note: for comparison purposes, here is a description of a vagrant:

"In the avian world, a vagrant is defined as a bird which is often found straying into a place beyond their normal known geographical range. Vagrancy is often characterised by the bird's random and unpredictable appearance at a location. Migrants or seasonal migrants meanwhile would appear from time to time during certain seasons, and repeatedly over a period of several years"

Here is a trio of Curlews in non breeding colors.

A Great Knot with Bar-tailed Godwits

Asian Dowitcher (left) and Bar-tailed Godwit (right)

An Asian Dowitcher showing its plain underwing

Such moment will be cherished by most birders

A huge flock of Great Knots seen over Kapar coastline

An Asian Dowitcher with a bunch of Brown-Headed Gulls

"You can run but you cannot hide"

The thing about wader watching is the thrill of searching for "odd balls" among the common waders. There is a Kentish Plover hiding among the many waders in the above photo.

Most waders would appear as a whitish blob from the front.

But if you view them from the the top they can be well blended with the mudflats as can be seen from the above photo.

The current status for Curlew Sandpiper is "Near Threatened" as compared to Broad-billed Sandpiper.

Here is a Broad-billed Sandpiper among the Lesser Sand Plovers

A Lesser Sand Plover (right) and a Kentish Plover (left)

In order to get as close as possible to the waders, i would try to hide among any vegetation which sprouts out from the vast open mudflats. 

For the above photo, i hid behind a large log but there is always a comfort zone line drawn by the waders beyond which they will start moving away as shown by the photo below. 

The closest i got to them was about 10 meters (30 feet).

A Common Sandpiper seen on the mudflat. They are usually solitary as i have observed.

The underwing pattern of a Red-necked Stint appears like a shearwater.

Lots of "krabby patties" to generate enough fat and strength for their return journey.

Whimbrel

The intricate underwings of a Whimbrel

Whimbrels

Whimbrel @ Kapar

Whimbrel goes crab hunting

Eurasian Curlews

The underwings of a Eurasian Curlew looks quite plain as well.

According to Don Taylor (2014), the timing of moult is dependent on a wide range of interrelated factors such as the bird's age, the latitudes of the breeding and wintering areas, the timing of the breeding season, length of migration and the availability of food concentration. Bar-tailed Godwit  (above) and Grey Plover (Black-bellied Plover) usually molt at staging posts. Most waders that have a complete moult on the breeding grounds are sedentary species or short-distance migrants. 

Meanwhile long-distance migrant waders such as Pacific Golden Plovers (above) and Wood Sandpipers, have a partial wing moult on the breeding grounds (i.e replacing the outer primaries and inner secondaries only), and then suspending the moult until they reach their wintering areas (Don Taylor, 2014).

Here is a unique phenomenon which i have observed recently. The above arrangement appears like an unwritten hierarchy for the waders whereby the bigger waders (the curlews) occupy the lower ground area while the Bar-tailed Godwit occupies the second tier and lastly the much smaller Whimbrels at the top. Amazing !

A group of Caspian Terns with some Grey Plovers (Black Bellied Plover) and Curlews

Some of them are already displaying breeding colors.

Very soon (most likely late April or Mid May) the waders will start their journey home. Their biological instinct will tell them the exact moment to leave. 

UNTIL WE MEET AGAIN NEXT WINTER !