13 - magpie anatomy and diet

It is a crisp, sunny winter's morning, and we have opened the doors to the garden. IA took this occasion to wander into the living room and looked if we had dropped anything edible on the tiled floor. This is a first, wandering into our house to graze. This time of year lawn beetles have gone through their lifecycle, and the magpies have spent less time foraging in our garden of late, so maybe this is why IA ventured indoors. As magpies are omnivores and as there is no shortage of food they can forage on, this behaviour could also be attributed to curiosity or opportunism. Today I am writing about some findings regarding magpie anatomy, how they find food underground, and about their diet.

IA listening-in on her food / foraging in our garden

Magpies have a hard and relatively thick, 'all-purpose' beak, with a pointed tip. Their beak works equally well for feeding on plant matter, as for crushing beetles that have a hard shell, breaking open hard soil, or fighting. Magpies can injure or even kill an intruder with their beak.

The much shorter beak of nestlings grows to adult size, by the time they are three months old.
I learned this fact from an excellent book that I just bought: 'The Australian Magpie - Biology and Behaviour of an Unusual Songbird', by Gisela Kaplan (see http://www.une.edu.au/__data/assets/pdf_file/0004/65551/MagpieBookCSIRO.pdf and/or http://www.publish.csiro.au/pid/3880.htm). Professor Kaplan is a researcher and teaches at the Centre for Neuroscience and Animal Behaviour at the University of New England, Armidale, NSW (Australia). She has studied magpies for well over ten years and has spent thousands of hours observing these birds. I can highly recommend her book, and am quoting from Professor Kaplan's findings about magpie anatomy and diet in the following paragraphs.

Even though the ability to fly imposes anatomical restrictions, it also means that flight has enabled birds to colonise nearly all habitats on earth, including islands. From  the magpie book I learned that the anatomical adaptation to a habitat is called adaptive radiation, and that restrictions have paradoxically produced a very high degree of variation: there are nearly 9000 species of birds, with a great variety of colouration, locomotion, feeding etc.

I have mentioned beaks, but did you know that birds do not have sweat glands, although water loss through the skin has been observed in some bird species. Magpies therefore control heat by rapid respiration where there is a very high load of heat. Magpies can also cool off and get rid of some heat through changes in skin blood flow, and they do this by positioning their feathers in a certain way and by lifting their wings. As an aside, because magpie nests are high up in trees and usually exposed to the elements, the female adult shields her brood by standing over them with her wings outspread, to provide shade from the sun or protection from heavy rain.

Magpies close their eyelids from the bottom lid upwards, usually only when they sleep or when they are in great pain. From Professor Kaplan's book I also learned that, in order to moisturise their eyes, birds have a third eyelid, called the nicitating membrane, that traverses the eye from the lower inner part outwards and up.

With regards to the head, magpies (like most corvids) have a very large upper hyperstriatum, also called 'wulst', in their large brain. This wulst is the area where visual information is processed and could mean that the magpie's long-distance vision is excellent and its acuity superior to that of an average human. I have observed my magpie family emitting alarm calls when they spotted eagles that were high up in the sky. The birds' hearing is also excellent, and they use it to great effect for locating food such as scarab larvae underground. This brings us to the magpie diet.

Foods consumed by Australian magpies
Magpies forage on the ground, and only feed above ground during breeding time when they feed their nestlings. Else trees are for roosting and breeding as far as magpies are concerned. When IA and IB were fledglings, I saw them walk with their parents on garden lawns and learning to forage. Magpies have a very varied diet, and substantial skills in acquiring their food items.
I already mentioned that they listen to the very slight sounds that larvae and earthworms make underground. Professor Kaplan refers to a study by Floyd and Woodland in 1981, that furnished conclusive proof that magpies find scarab larvae by sound (and sometimes vibrations) alone, and not by visual or olfactory clues. She writes that the researchers had recorded the minute sounds of movements made by scarab larvae and then, using minute speakers buried underground, playing back the recorded sounds. The magpies detected the sounds, located and digged up the speakers!

This 'listening' for food has to be learned and therefore fledgling magpies walk close to the adults, learning to link this sound to food.

Apart from earthworms, beetles and larvae, magpie also eat invertebrates such as snails, millipedes, mantids, crickets, grasshoppers, weevils, bees, at least eight varieties of ant, moths, crustaceans, spiders, scorpions, and all manner of insects.

They also eat reptilians and amphibians such as skinks, and frogs, and mammals such as mice and other small rodents.

To round up magpie diet, being omnivores they also like plant matter, such as seeds, grains, tubers, walnuts, figs and prickly pears.