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Episode 298: Bemused by the Blue Footed Booby

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Two blue footed Boobies (Sula nebouxi) helpfully displaying their iconic aquamarine blue feet for the camera (image from charismaticplanet.com)

It doesn’t get much more distinctive than having bright, aquamarine blue feet, and these colourful features make the aptly named blue footed booby a favourite of birders and visitors to their Galapagos Island home. First described in the 1880’s by French naturalist Alphonse Milne-Edwards, their name is derived from the Spanish word ‘bobo’ meaning foolish or clown; perhaps a little mean but given to them in honour of their clumsy waddling nature on land and the fact that they seem to have a rather stupid lack of fear when it comes to humans. There are two recognised subspecies today: Sula nebouxi nebouxi, found along the Pacific coast of Southern and Middle America, and Sula nebouxi excisa, iconic inhabitant of the natural wonder of the Galapagos Islands.

Blue Footed Boobies are one of three species found on the Galapagos Islands, along with the Red Footed Boobies and the Nazca Booby. They may be seen as clumsy clowns on land, but they are pretty agile on the wing. They cruise through the skies, searching the waters below for schools of fish like sardines or mackerels, an essential part of their diet. When they spot a snack, they fold their wings back and plunge dive into the water, from heights anywhere between 10 and 100 metres, hitting speeds of up to 97 kilometres per hour. Hitting water at these speeds is like smashing into a brick wall, so Boobies have specially evolved air sacs in their skulls that protect their brains from the massive pressure. Not so clumsy anymore!

An amazing action shot of a Blue Footed Booby diving after a fish (image from WWF.org)

Feeling blue? Blue Footed Booby Courtship

Scientists uncovered how Blue-Footed Boobies have such fancy feet; specialised collagen fibres, modified by carotenoid pigments from their sardine-based diet, give the famous bright blue colouration. Carotenoids actually act as antioxidants, soaking up harmful toxins from the body and stimulating the immune system, and so in Boobies, the brighter the feet, the healthier the bird. In lab experiments, boobies that were deprived of good quality food for up to 48 hours ended up with dull feet, as the lipids and proteins needed from their food to absorb and transport the pigments were reduced.

Why exactly do Blue-Footed Boobies have blue feet? From the research done on the pigments and condition of the bird, scientists deduced that the blue feet are a kind of visible health check. The bluer the feet, the better. The blue colouration has evolved as a way for female birds to select the best males. In fact, it is the single most important feature a female will take notice of in breeding season. In an experiment to test the role of blue feet in breeding, researchers painted the feet of the males after their partner had laid an egg to make their colour duller. Just a few days later, the female would lay a second, much smaller egg, with less yolk, a vital factor in the development, hatching and survival of the chick. The brightness of the feet is so important that when a female sees a duller colour, she will invest less energy in the egg. Dull feet equal poorer health and genetic quality, and so the female won’t provide as many resources to the offspring.

Fancy feet: an up-close shot of the magnificent blue flippers. (image from galapagosconservation.org.uk)

Males also have an eye for colour. They judge the colour of the eggs the female has laid; the bigger and brighter the eggs are, the better condition they are in, and therefore the healthier the mother is, and this will be passed onto the offspring. They also judge the blueness of feet; in another experiment, researchers painted clutches of eggs a dull colour, but found that males would still invest significant time caring for them if the female had lovely aquamarine feet. It’s a harsh time in the world of Blue-Footed Booby relationships!

Its not all feet fancying though; male boobies also have a high stepping mating dance that they trot out when they want to impress the ladies even more. They raise each foot one at a time, called sky-pointing, accompanying this tantalising flash of their perfect shade of blue feet with horizontally extended wings, raised heads and a long call.

Inspiring Islands: the lands that shaped Charles Darwin

Fortunately, the Blue-Footed Booby is currently listed as least concern by the IUCN, largely because the species has such a large range. However, the species is in decline, although currently the drop in population size isn’t considered worrying enough to re-classify the birds. Despite this, populations in the Galapagos Islands have dropped by 50% in the last 20 years, with these declines blamed on the sudden disappearance of sardines in the bird’s diet. Between 2011 and 2013, barely any birds bred, and few juveniles were sighted in the usual breeding colonies. Sardines are particularly important for Blue Footed Boobies; they are rich in the vital antioxidant compounds the birds need to keep themselves healthy and their feet nice and bright. No-one has exactly pinpointed what is happening to the sardine schools around the Galapagos Islands, with suggestions ranging from over-fishing to increasingly extreme fluctuations in El Niño events, a climate pattern that sees unusually warm surface waters in the Pacific Ocean. Although the population in the Galapagos is still relatively large, there are still worries that the breeding colonies have never fully recovered from these crashes between 2011 and 2013.

Blue Footed Boobies are bioindicator species. This means that fluctuations in their health (easily visible in the blue of their feet) and population sizes are indicators of the health of their environment. When levels of prey fluctuate, Boobies will change their diet and the growth rate of chicks accordingly. This makes them an important conservation tool.

Although Blue Footed Boobies appear to be doing okay for the time, it is still vitally important to protect their habitats, in particular the amazing and unique ecosystem of the Galapagos islands. Not only can you spy Blue-Footed Boobies cruising around the islands, you can also see the Galapagos Giant Tortoise, Galapagos Iguanas, Galapagos sea lions and the famous finches that so inspired Charles Darwin to develop his theory of evolution, to name just a few.

A snapshot of the dramatic coastline of the Galapagos Island. (Image from latinrootstravel.com)

Like so many island ecosystems, the Galapagos Islands are an incredibly fragile jewel in the Pacific Ocean. The high levels of unique biodiversity are particularly threatened by invasive species, as species have evolved away from the pressures faced by mainland species and have little to no tolerance to new species that swoop in and outcompete them for resources. One particularly dangerous species is the parasitic fly Philornis downsi, whose larvae feed on the eggs and hatchlings of many Galapagos birds, leading to total nest failures in many cases. Increasing tourism and a rise in the number of permanent residents, going from just 2000 in the 1950s to almost 30,000 today, has meant that pollution and waste management are a growing issue. This increasing human footprint on these fragile islands is also leading to unsustainable urban development, although local authorities have recognised this problem and are increasing restrictions on new developments. Of particular concern for our Blue Footed friends is the issue of overfishing in the waters of the Galapagos, which are some of the most environmentally sensitive in the world.

Conservation optimism

The uniqueness of these Pacific Islands has long been recognised as in need of protecting, and there are many laws and policies in place to keep the ecosystems as pure as they can be. As long ago as 1986, the waters around the Galapagos were established as a marine reserve and in 2021 the president of Ecuador announced an expansion of the reserve to cover another 60,000 square kilometres, including the Cocos Ridge, a vital migration route for sharks and turtles. Re:wild, a conservation organisation founded by Global Wildlife Conservation and the vary famous, once teenage heartthrob Leonardo DiCaprio, raised 40 million dollars to restore degraded habitats in 2021. There are strict laws for tourists visiting the Island, and if you do fancy the trip of a lifetime, make sure you familiarise yourself with these rules at https://www.galapagos.org/travel/park-rules/.

The range of the vitally important marine reserve in the waters around the Galapagos Islands. (image from galapagosconservation.org.uk)

The only UK charity solely focusing on conservation and sustainable futures on the Galapagos Islands is the Galapagos Conservation Trust (GCT). They raise funds and awareness and partner with Ecuadorian authorities, NGOs, communities and local scientists to carry out research and deliver projects across the Islands. You can check out their current and past projects at https://galapagosconservation.org.uk/what-we-do/projects/.

They have a ton of different ways you can get involved to help conservation in the Galapagos Islands from becoming a member, donating, adopting a Galapagos animal, shopping on their gift store, or joining one of their annual cruises. Check them out at https://galapagosconservation.org.uk/get-involved/.

Awesome videos!

References

Anderson, D. (2014) ‘Chronic lack of breeding by Galapagod Blue-footed Boobies and associated population declines.’ Avian Conservation and Biology.

Detressangle,F. Boeck, L. Torres, R. (2008). ‘Maternal investment in eggs is affected by male feet colour and breeding conditions in the Blue Footed Booby.’ Journal of Animal Ecology.

https://www.americanoceans.org/facts/blue-footed-booby-feet/

Blue-footed Booby

Morales, J. Roxana, T. and Velando, A. (2012) ‘Safe betting: males help dull females only when they raise high quality offspring.’ Behavioural Ecology and Sociobiology.

Torres, R. and Velando, A. (2007) ‘Male reproductive senescence: the price of immune-induced oxidative damage on sexual attractiveness in the blue-footed booby.’ Journal of Animal Ecology.

Velando, A. Beamonte-Barrientos, R. and Torres, R. (2006) ‘Pigment-based skin colour in the Blue-footed Booby; an honest signal of current condition used by females to adjust reproductive investment.’ Oecologia.

Zavalaga, C.B. Benvenuti, S. Dall’Antonia, L. Emslie, S.D. (2007) ‘Diving behaviour of blue footed boobies in northern Peru in relation to sex, body size and prey type.’ Marine Ecology Progress Series.

MASSIVE THANK YOU TO RACHAEL DA SILVA FROM THE UK FOR THIS WRITE UP! PLEASE FOLLOW HER ON INSTAGRAM AND HER WILDLIFE ARTWORK AT TILLY_MINT08

November 20, 2022
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