A technique to measure the volume of diving birds during voluntary dives

Research output: Contribution to journalArticlepeer-review


Buoyancy has a substantial contribution to the total mechanical cost of diving in waterbirds. Most of the techniques currently employed to estimate buoyancy are based on measuring the volume of carcasses or forcibly submerged birds using the water displacement (Archimedes) principle. In such techniques, the voluntary control the bird might have over plumage and respiratory air volumes is neglected. Here, I propose an adjustment to the water displacement measurement that allows the measurement of buoyancy in real-time from unrestrained live birds diving voluntarily. The novelty and accuracy of the technique lie in using a pressure sensor to continuously measure the water level inside the dive tank while filtering out the interference from surface waves. The error of the volume measurement in the proposed technique was only ±2.4%. Feasibility of measurement is demonstrated on captive Great Cormorants (Phalacrocorax carbo sinensis). The measured volumes of Great Cormorants exceeded predictions made based on the volume of carcasses and on average resembled values measured from live restrained birds. However the technique highlighted the high variation in buoyancy of live birds (up to 30%) as a result of small changes in the air volumes taken with the bird underwater.

Original languageEnglish
Pages (from-to)963-969
Number of pages7
JournalJournal fur Ornithologie
Issue number4
StatePublished - 2010
Externally publishedYes


  • Buoyancy
  • Plumage air
  • Volume measurement
  • Waterbirds


Dive into the research topics of 'A technique to measure the volume of diving birds during voluntary dives'. Together they form a unique fingerprint.

Cite this