Hawk Conservancy Trust Newsletter Spring 2021 Issue 87

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HAWKTALK SPRING 2021 ISSUE 87

HAWKTALK SPRING 2021 ISSUE 87

Brilliant bird beaks

In review

WHAT’S HAPPENING IN THE WORLD OF BIRDS OF PREY?

For birds of prey, their beak is one of their most important tools for survival. Beaks come in all shapes and sizes and they can give us clues to the types of food that bird eats, and how. One common characteristic of all birds of prey is that their beaks are curved. Can you match the beak images This eagle is skilled at catching prey with its huge talons. It also scavenges and its big and powerful beak can tear into the tough hides of large carcasses. HOODED VULTURE Hooded Vultures have small, thin beaks, perfectly adapted for quickly picking and eating small scraps from carcasses, and reaching into small spaces to grab morsels of meat. BARN OWL This species has a short, curved beak. It swallows small prey items whole, and coughs up undigested parts such as fur and bones as a pellet later. The beak is also perfect for tearing larger prey items while gripping with their talons. KESTREL This species has a short, stout beak for eating small prey such as small mammals, birds, worms and insects. Falcons also have a notch in their beak called a ‘tomial tooth’. RED KITE The sharp, hooked beak which is the perfect size and shape for a varied diet, helping them scavenge for food as well as eating things like insects and small mammals. to the bird of prey? STELLER’S SEA-EAGLE

LATEST RESEARCH Could use of rat poison be a cause of Kestrel declines? Rats and mice are controlled using Second Generation Anticoagulant Rodenticides (rat poison) to reduce agricultural damage. However, when predators prey on rodents that have eaten rat poison, they too are exposed to the toxins, which can be lethal. This study investigated whether use of rodenticides may have contributed to the recent widespread declines of Kestrels across the UK. The researchers found that more than 66 percent of Kestrels tested between 1997 and 2012 had traces of at least one rodenticide in their livers! Adult Kestrels had higher concentrations than younger birds, suggesting that the toxins accumulate in the birds’ bodies over the course of their lives. They also found a negative correlation between Kestrel population size in any given year and the concentration of rodenticides in the livers of Kestrels in the same year, which suggests that these poisons may have a population-limiting effect on Kestrels. This work is significant because it sheds light on the recent declines of Kestrels, however it also indicates that further work is urgently needed to examine in more detail the effects of rodenticides on Kestrels and other raptors. Roos, S., Campbell, S.T., Hartley, G., Shore, R. F., Walker, L. A., Wilson, J. D. (2021) Annual abundance of common Kestrels ( Falco tinnunculus ) is negatively associated with second generation anticoagulant rodenticides. Ecotoxicology . https://doi.org/10.1007/s10646-021-02374-w Snowy Owls are nomadic breeders, and it is assumed that they will sample different patches by making stopovers as they migrate in order to select summer breeding sites. Scientists examined the spring migratory movements of nomadic Snowy Owls in the USA and Canada to determine whether the sex or age of birds affects when and for how long they make stopovers. To do this they fitted 24 Snowy Owls with GPS trackers during the overwintering period to follow their movements. They found: • both adults and immature birds departed for migration around the same time • adults completed migration earlier than young birds • there was no difference between the age classes • all owls were more likely to make a stopover at the beginning of the migratory route, usually to forage or roost. These results suggest that Snowy Owls use stopovers to build up reserves, and rest, while on migration. The infrequent use of stopovers later in the migration, while in their summer range, suggests that the owls are able to select summer breeding sites via short overflights without the need to sample different patches extensively when looking for a place to breed or settle. Brown, A., McCabe, R. A., Therrien, J., Wiebe, K. L., Weidensaul, S., Brinker, D., Gauthier, G., Elliott, K. H. (2021) Nomadic breeders Snowy Owls ( Bubo scandiacus ) do not use stopovers to sample the summer environment. Ibis. doi: 10.1111/ibi.12950 Why do Snowy Owls make stopovers on their spring migration?

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IN PRINT Back to Nature, by Chris Packham and Megan McCubbin This book is a wonderful combination of nature magic, inspiring real-life conservation, and thought-provoking realisations about the state of the planet. It explores the importance of nature and wildlife for human wellbeing, and very effectively throws

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light on the awful truths about biodiversity loss, the climate crisis and the role we must all play to attempt to reverse the damage. Highly recommended, whether you are a seasoned conservationist, or just have an interest in the natural world.

Signed copies available from the Trust shop

WORTH A WATCH Birdsong Lessons with Lucy Lapwing

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‘Hear lots of birds singing, but haven’t got a clue who’s who?’ Lucy Lapwing has a new YouTube series of short, informative and funny videos to help you on your birdsong learning journey! A brilliant resource for complete beginner birders, or those with a bit of birdsong knowledge under their belts looking to brush up. How many have you learnt so far? If you would like to hear more from Lucy Lapwing, go to youtube.com/LucyLapwing. She also featured on the February episode of our podcast Nature’s a Hoot, where Tom and Hannah chat to her about science communication and getting nerdy about nature. You can listen to this wherever you get your podcasts.

Adult male Snail Kite (Rostrhamus sociabilis)

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fun facts Snail Kites have one of the most hooked beaks in the world of birds of prey. Their beaks have actually evolved and adapted to allow them to eat their preferred prey of snails with ease! Birds of prey have a special, sharp lump on the top of their beak known as an egg tooth. They use it to break their way out of their shell at hatching. This process can take up to three days! Soon after hatching, they lose this egg tooth.

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Answers

D. Steller’s Sea-Eagle, E. Hooded Vulture

Brilliant bird beaks: A. Barn Owl, B. Red Kite, C. Kestrel,