‘Insights’ presents stimulating questions about bird behaviour and is designed to develop an awareness of the complexity of bird life.

It is difficult to provide concise answers to the questions below as many factors combine to help us determine bird behaviour. But to get the ball rolling, here are some insights to ponder. Perhaps readers would like to propose extra reasons and details that might help form plausible answers. Please feel free to e-mail your answers and also pose new questions.

This page will be updated periodically.

 

What is a bird’s eye view?

Who knows for sure what birds see? The complex anatomical arrangement of a bird’s eye and the remarkable processing ability in its brain and the fact that its image acuity is an adaptive trait make avian vision an absorbing study. Here we describe, albeit somewhat simply, some features to consider when thinking about how birds see.

Among birds, raptors have exceptionally keen eyesight. They are able to resolve details at distances 2.5 to 3 times further than humans — an impressive feat. They also have binocular vision (their binocular overlap is between 35 and 50%), which gives them acute depth perception — useful when they perform quick manoeuvres while chasing prey.

In many birds, the huge number(between 400,000/mm2 and 1 million/mm2) of light receptor cells in the retina (highest number

located specifically in the central and temporal foveae) makes it possible for birds to see sharp images regardless of the direction and intensity of the light source. In addition, the muscles of the eye that control lens curvature and the aperture of the pupil permit pin-point focusing and fast tracking as well as quick adjustment to varying light conditions. Various studies indicate that, in some birds, visual information gathered from each eye and processed in the brain might be used for different tasks. Many birds are also capable of seeing in the UV spectrum — an ability humans lack.

Spend some time watching a bird in search of prey; note the position of the eyes in the skull and their size, the posture of the bird, its head movements, the position of the head when the bird flies, and its foraging environment. Look at a variety of species in this manner. Gather as many contextual clues as possible to help you understand how they perceive the world.

 
Why do birds join mixed species flocks?

At a glance it would appear that the two species, pictured left, join forces to forage together to exploit nectar-rich resources. But could there be any other benefits that might bring these two species together?

To find out, watch what each species does when it alights in a tree. Follow closely a few individuals of each species and note whether both species forage; if so, do their foraging styles differ? Other things to note include the age of the birds, their position in the tree (is there partitioning of resources?), the tree’s proximity to other flowering trees, the time of day, the state and similarity of their plumage, the calls that they emit, their response to other flock members’ calls or body postures and how frequently they check their surroundings. Are there dominant individuals and if so how do other flock members respond to them? Are there predators about?

An astute observer will learn much from this exercise.

 
What provokes early morning bird song?

Many song birds sing early in the morning. The factors that influence this phenomenon may be broken up into three categories: 1) environmental conditions, e.g. humidity, temperature, light levels, wind speed, environmental noise, prey activity; 2) mood of the bird, e.g. its hormonal levels, its health, its energy budget and 3)social interaction, e.g. proximity of neighbours, presence of potential mates and rivals and raptor presence/absence.

Listen to specific birds as they sing in the early morning (kookaburras are among the first to commence the dawn chorus). Write down all that you know about them and think about some of the factors that might be influencing their singing. Can you think of others?

 

Why do magpies strike this pose?

The answer to this question is fairly easy; however gaining an insight into how this behaviour might have evolved is exciting and challenging. When reflecting on your answer, consider such contextual clues as the size and shape of the magpie’s beak, its diet, its foraging strategies, its predators and territorial competitors, where it lives, and its social behaviour. Is it a migratory species?

We all know that magpies are territorial, frequently staking a claim that may include manicured suburban lawns or parklands —perfect sites for bird watching (you don’t have to travel to enjoy the mysterious life of birds!).

Enjoy some time in your garden or local park and unravel the complexity of magpies and their foraging and prey capture strategies.

 

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