Ravi Sankaran and K. Sivakumar studied the Nicobar megapode with a layered field program: they mapped islands and counted active incubation mounds, then measured mound temperature and decomposition while recording the birds’ social behaviour. Sankaran’s 1994 survey created the pre-tsunami baseline; Sivakumar’s 2006 resurvey showed how severely the 2004 Indian Ocean tsunami reduced breeding populations.
Why the researchers counted mounds instead of birds
Nicobar megapodes are shy and difficult to detect directly. Their incubation mounds, however, remain in place and provide visible evidence of breeding activity. Active-mound counts therefore became the practical monitoring unit for distribution and abundance.
The approach does not mean one mound equals one pair. Later observations showed that several pairs could use the same mound, so mound counts had to be interpreted alongside information about social organisation and breeding populations.
Sankaran’s 1994 island-wide baseline
Sankaran surveyed the Nicobar Islands to determine where the species occurred and to count active mounds. His 1994 sampling covered 127 active mounds of M. n. abbotti and 85 active mounds of M. n. nicobariensis.
#1 Best Overall
| Population measure | M. n. abbotti | M. n. nicobariensis |
|---|---|---|
| Active mounds estimated from the 1994 survey | 849 | 312 |
| Adult population estimate | 4,500–8,000 adults total, reported by Ravi Sankaran in 1995 from the 1994 survey | |
This baseline supplied both a geographic picture and a numerical reference for later assessment. It also identified habitat loss as the main long-term threat, particularly conversion of coastal forest to coconut plantations. Urbanisation and coastal roads damaged habitat as well, while hunting and egg collection added direct pressure.
What the 1999 mound study examined
In the 1999 paper “Preliminary results of an ongoing study of the Nicobar megapode,” Sankaran and Sivakumar moved beyond counting mounds. They examined how mounds function as incubation systems and how birds organise themselves around them.
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Mound structure and heat production
- Mound dimensions: measurements were used to assess how physical size affects incubation conditions.
- Microbial decomposition: decomposition of organic material was considered the probable major heat source.
- Temperature: the researchers measured incubation temperatures and found that mound size was the most important factor in keeping temperatures within optimal levels.
The study did not demonstrate a direct relationship between the rate of microbial activity and mound temperature. Its conclusion was therefore cautious: decomposition probably supplies much of the heat, but mound size appears to be the key stabilising factor.
Social organisation around a mound
Field observations recorded multiple pairs using one mound, territorial behaviour, extrapair copulations and pair break-up. These findings showed that a mound is a shared breeding resource within a social system, not simply a nest belonging to one permanent pair. The observations allowed the authors to discuss the species’ mating system rather than infer it from mound occupancy alone.
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How Sivakumar measured the tsunami’s impact
After the 2004 Indian Ocean tsunami, Sivakumar repeated status and distribution work. The 2006 survey could be compared with Sankaran’s known pre-tsunami baseline, creating a before-and-after assessment rather than a single post-disaster snapshot.
| Research phase | Timing | Main measurements | Result |
|---|---|---|---|
| Baseline survey by Sankaran | 1994 survey, reported in 1995 | Island distribution, active incubation mounds and adult abundance | 2,318–4,056 breeding pairs as the baseline later reported by Sivakumar (2009); 4,500–8,000 adults in Sankaran’s 1995 estimate |
| Post-tsunami survey by Sivakumar | 2006 survey, reported in 2009 | Repeat status, distribution and breeding assessment | 395–790 breeding pairs, about a 70% decline from the baseline |
Populations on Megapode Island and Trax Island were considered wiped out by the tsunami. The disaster caused acute inundation and loss of coastal habitat on top of the chronic pressures already identified in the 1995 survey.
Why the comparison was scientifically useful
Because the earlier survey had established where mounds and birds were found before the disaster, the later work had a counterfactual reference: researchers could estimate what had changed after the tsunami instead of relying on recollection or an unmatched count. Sivakumar also warned that poorly planned coastal restoration could create further damage, since nesting habitat is concentrated near the shore.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the habitat evidence says about conservation
The mound surveys identified coastal forest as essential habitat, and a later habitat-suitability study reinforces that pattern. In the 2026 Journal for Nature Conservation study, distance from the beach accounted for 60.3% of model importance, followed by canopy height at 13.4%, elevation at 9.1% and distance from a road at 6.6%.
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- Houghton Mifflin Field Guide to Birds of N.A. by Kaufman Field Guides - 0-618-57423-9
| Habitat variable | Model importance |
|---|---|
| Distance from beach | 60.3% |
| Canopy height | 13.4% |
| Elevation | 9.1% |
| Distance from road | 6.6% |
These values do not replace field counts, but they help explain why coastal development, roads and restoration design can have disproportionate effects on a bird whose breeding sites cluster near the shoreline.
Quick Recap
What the combined program established
- Active incubation mounds are the most practical observable unit for a cryptic species.
- Sankaran’s 1994 work supplied the island-wide pre-tsunami distribution and abundance baseline.
- Mound size, decomposition and temperature must be studied together to understand how eggs are incubated.
- Multiple-pair mound use and territorial and mating observations reveal a social system more complex than one pair per nest.
- Sivakumar’s repeat survey quantified the tsunami-era collapse and identified islands where populations disappeared.
- Protecting coastal forest, limiting habitat conversion and controlling hunting and egg collection address both chronic and disaster-related risks.
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