Northern royal albatrosses counted from space

Albatross is the large seabird family which include 24 known species.The Northern royal albatross is a large seabird species of this  family with wingspan up to 3.7 m. It appeared in Oligocene and has a lifespan of 42 years. It is the most threatened species in the Albatross family due to change in environment and  anthropogenic activities. Primary food source are fishes and due to overfishing in this area Northern royal albatross population is decreasing and also the baited longline gear used by some vessels has an unpleasant knack for attracting foragers and pulling them underwater where they drown. These species are found only on the  Chatham Islands sea-stacks especially on the Sisters and Forty Fours Island and one big storm rolls through at the wrong time of year, can severely wash breeding success.

                                        Location map of the Sisters and Forty Fours Islands. © Google Earth.

A group of scientist adopted a methodology in which they have used high-resolution satellite imagery to gauge the numbers of Northern royal albatross.The  government of US has also permitted such keen resolution to be distributed other than military and intelligence sectors.This methodology was tested at Bird Island, South Georgia. The team slightly over-counted the birds as non-breeding birds were also captured in a satellite image. Applying the same technique at the Chatham Islands, the team used WorldView-3 satellite courtesy of DigitalGlobe imageries and counted 3,600 nests which are slightly lower the manual count of 5,700 in 2009. It was very difficult to count albatrosses as they are only over a metre in length, but high-resolution imageries of WorldView-3 capture features as small as 30 cm. White plumages are clearly visible in the image, these are Northern royal albatross, either sitting on the eggs to incubate or guarding newly hatched chicks.The team counted these dots and estimate the total number of albatrosses. 

                                                                             ©DigitalGlobe

Satellite technology is used because nesting sites are so inaccessible. Manual counting is very difficult because the nests are at the top of the vertical cliffs and getting the people, ships or planes to these islands is expensive. Weather is also a major problem here as it doesn't allow planes to fly over it. Strong wind and dense cloud prevent flying and researchers have to wait until it clears which is time-consuming. Therefore satellite technology is used  which  is cheaper, more reliable and less time-consuming. 

Dr.Fretwell, the scientist of this project said that the population of the Northern royal albatrosses are decreasing as the count of breading Northern royal  albatrosses were much lower than anticipated. He also added that it could be a poor year for breading, so they required continuously satellite data of few  coming years to monitor the population of this species.

                                             Inaccessible nests of Northern royal a lbatrosses. © Paul Scofield