The male Bar-tailed Godwit (Limosa lapponica) , known as BBRW set a new world’s flight record on 27 September 2020.
This male godwit BBRW had taken off from the coast of southwest Alaska over nine days earlier. Now, 12,000 km later, his feet were to touch land again for the first time since departure. It is a feat of endurance and stamina that until recently many biologists considered to be physically impossible. Yet this bird was just the latest to contradict that view.
BBRW had been one of 20 adult godwits fitted with satellite tags at Pukorokoro Miranda Shorebird Center, New Zealand, in November 2019. From March 2020 the birds were tracked northwards to Alaska via refueling stopover sites around the Yellow Sea. By August only ten of the tags were still operating. Four of these birds including BBRW departed from the Kuskokwim Shoals in southwest Alaska on 18 September. These departures took place over a five-hour period presumably in four separate flocks. South of the Aleutians they had to battle head winds, before strong easterly winds began pushing the birds westward of the direct path to New Zealand.
At times, the paths of the four birds with transmitters were over 500 km apart.
Their course showed them headed for New Caledonia, where two other tracked birds had stopped earlier. Yet three of the godwits then changed track and headed straight for New Zealand. At times BBRW was rocketing along with a 40-45 km/h tail wind, and groundspeed of 80-90 km/h. When he landed at Pukorokoro at around 2130 on 27 September, he had travelled at least 12,050 km in nine days and seven hours. This broke the 11,680 km record of E7, the famous female godwit whose flight from Alaska in 2007 had finally proved what some people had suspected: that a nonstop flight bridging the length of the Pacific was possible.
Tiny cardio-vascular systems burning brown fat are the engines for these mammoth journeys. To store sufficient fuel, birds need to double their weight before departure. Prior to migration flights they undergo physiological and biochemical changes within their bodies: expanding the digestive system to full capacity, developing more red blood cells to carry lipids to where they are needed to build tissue, and shrinking non-essential organs immediately before departure. The essential factor making all this possible is abundant food, and healthy intertidal flats where that food is found.
In their annual cycle, bar-tailed godwits link widely separated locations. Tidal flats in New Zealand and Australia are where they moult and prepare for northward migration; similar habitats in the Yellow Sea region are where they refuel during migration, enabling them to arrive on their Arctic breeding grounds in good condition for breeding; and the superrich mudflats of the Kuskokwim Shoals is where they find the quantities of fuel needed for that trans-Pacific journey.
In 2005 researchers at the USGS Alaska Science Centre began a program to deploy satellite transmitters in godwits. This finally bore fruit with the epic journey of E7 in 2007. This latest tracking project involved a team of researchers as widely dispersed as the tidal flats the birds depend on, including the Global Flyway Network based in the Netherlands, Massey University in New Zealand, Max Planck Institute in Germany, Birds Canada, Fudan University, China, and Pukorokoro Miranda Naturalists’ Trust.
