Black-thighed Falconet hunting during nesting

The mating and nesting rituals of a pair of Black-thighed Falconet (Microhierax fringillarius) have already been posted earlier by Connie Khoo: see HERE. The current post, also by Connie, involves the strange hunting behaviour of this pair of falconets during their nesting period as observed in early February 2007.

The pair of nesting Black-thighed Falconet had already established an eyrie or nest on the limestone cliff. So it appeared strange that they were observed collecting pieces of long dried grass. Also, these falconets are not known to make use of any nesting materials to line their nest. Through further observations, they were seen bringing these grass pieces to another site nearby, a sort of “false eyrie” (above right). A male falconet was later seen in the false eyrie with one eye closed and the other keeping watch on the ground below (above left). He would dive down the moment he spotted a foraging Eurasian Tree Sparrows (Passer montanus) on the ground below and returned to his eyrie to feed the chicks. These falconets are also adept at catching House Swifts (Apus affinis) on the wing.

A pair of these Eurasian Tree Sparrow was at the same time building their nest about 3 m below the false eyrie (left). Whenever a falconet brought back the dried grass, the sparrows would watch from inside their own nest or from somewhere nearby. Once the falconet flew off, one sparrows, usually the one outside the nest, would give a call and fly to the false eyrie, steal a piece of dried grass and returned to its nest. Sometimes both sparrows would be around the false eyrie looking for nesting materials when the falconets were not around. As soon as the falconet was sighted, the sparrows would fly off.

Now why did the falconets collect the dried grass and brought them to the false eyrie? Was the materials used to lure the sparrows? If so, why did they not pounce on the sparrows when the latter were stealing the grass pieces? Was it to build up the ‘trust’ of the sparrows before preying on them? And why did the falconets target the sparrows foraging on the ground below and not when they were stealing from the false eyrie? We need answers to these questions!

Note: Black-thighed Falconets usually make use of abandoned nest holes of barbets and woodpeckers. Occasionally they nest in holes under eves of buildings. No materials are used. Where they nest in tree holes, wood chips can be found but no other nesting materials are added. In other nesting holes, insect remains can be found. On limestone cliffs, these falconets seek out the many natural cavities on the limestone face.

All image by Connie Khoo.

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3 Responses

  1. Lee Chiu San

    Why do the falconets not hunt the sparrows in the nest close to theirs, whereas they hunt other sparrows further afield?

    Konrad Lorenz, one of the pioneers of the study of animal behavior, proposed a theory.

    He said that the hunting and killing instinct is suppressed at a home site. This sounds logical, and would be a natural development.

    Many carnivorous animals can be triggered, to a larger or smaller extent, by instinct. When presented with particular stimuli, they have a natural reflex inclination to strike or bite first without thinking.

    Carnivorous animals have impressive weaponry, and can inflict serious damage.

    The fluttering of a chick beginning to fledge could trigger such a reflex. So could an accidental brush or a push. It would serve no purpose if, at the usual resting place of a pack, one wolf were to stumble, brush into another, and end up in a fight resulting in serious injuries to both.

    Therefore, it would be helpful for the survival of carnivorous species if the hunting/killing instinct could be switched off in the place that they consider home.

    That instinct switches on again when the animals are away from home, where there would be more space between them to prevent accidental contact.

    There are many recorded instances of cats, which had lived peacefully for years in the same homes as dogs, suddenly being hunted and even killed by those same dogs when they met somewhere out on the streets.

    And experienced dog handlers know that no dog, not even one of a breed as mild as a cocker spaniel, can be trusted not to take an opportunistic bite when a child runs past in a field away from home – even if that child lives in the same home as that dog.

    I have read in an American ornithological article (which I cannot remember in which magazine) that it is not too unusual to find songbird nests in close proximity to those of raptors.

    Some songbirds might not require a large foraging area, and their total territory might still be within the limits of the raptor’s “no kill” zone.

    Konrad Lorenz said that at least with cats, they knew when they were outside the “no kill” zone, and would treat with circumspection even dogs they were familiar with.

    Do prey birds know how to measure the size of the “no kill” zones of their neighbouring predators and behave appropriately?

    As to the second point raised in this post, I cannot think of any reason why the falconets would bring grass to their nest site. Anyone else care to share other theories?

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  2. Fascinating stuff. Need to look deeper into these theories. Thanks Chiu San.

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  3. […] The mating and nesting rituals of a pair of Black-thighed Falconet (Microhierax fringillarius) have already been posted earlier by Connie Khoo: see HERE. The current post, also by Connie, involves the strange hunting behaviour of this pair of falconets during their nesting period as observed in early February 2007. The pair of nesting Black-thighed Falconet had already established an eyrie or nest on the limestone cliff. So it appeared strange that they were observed… Read More […]

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