Sunday, October 28, 2012

How to do an Eastern Spinebill population count in your area from poor quality videos

Let's say you have an Eastern Spinebill visiting your garden and you never see any more than one bird at a time. The chances of it being the same individual is about 50%. I actually thought there was only one individual visiting my garden but apparently there is at least two including one female. Taking videos of these birds is very helpful to help identify any different birds by their markings, which I will explain in a minute. Not everyone is going to have a really expensive camera nor take photos of these birds that come out crystal clear. Chances are your photos and videos will be blurry, out of focus or you just can't see the whole bird as it hides behind branches whilst feeding. These birds rarely keep still and are always moving about. But even if you do manage to get a clear shot it will probably be out of focus or blurred because you're trying to keep up with the bird by moving the camera. This is normal, and to date, this is what all my videos of these birds have come out like.

Image 1 Notice the white triangle on it's chest
Image 2 A near frontal view


Image 3 A side on view
I actually recommend just taking videos of these birds because not only do you pick up the sounds they make, you can also take a screenshot of the bird if it is crystal clear at any point in the video. I also recommend that you ignore the eye colouring of each bird, as when the sun light is shining into their eyes, their eyes turn white in colour which can be seen with the naked eye and it is picked up in video footage and photos. In the shade their eyes turn their natural colour, which I think is red or reddish brown. I'm not really sure actually.

Having Grevilleas out the front of my place is an added advantage as Eastern Spinebills feed on the nectar of the Grevilleas at least 3 times a day but only for a few minutes each time. They move on as quickly as they arrive. Studying these birds has told me that only sometimes do they call out. During the breeding season they call out a lot. It appears that they are keeping in contact with each other, as to where each other are. However, I have found a way to actually do a population count on this species but it involves taking videos every time I see these birds.

The most reliable way to do a population count is to check the birds' dark band markings that go from the back of their head down toward the chest. The formation of this dark band appears to be uniquely different with each individual bird despite the bird's age and gender. This dark band marking is similiar to our fingerprints - no fingerprints of 2 humans are the same. The same can be said for these dark band markings of this species. When studying your own videos of this species try to take screenshots of a near frontal view (see image 2) and a side view (see image 3) of each bird in the video. By getting a near frontal shot of the bird you will be able to tell how wide the dark band is and if there are any other unusual markings on the bird around the side of the throat and upper chest area. (See image 2 again)

In the last two photos we are looking at the same bird (see the dark band marking indents that go inward from the outside into the white area of the throat? They look like coloured in arrow heads. However, the bird in the first photo does not have these markings, and actually has a white patch of feathers that are on the outside (left and lower) of the dark band marking. It makes a triangle patch of white feathers between the dark band and the buff coloured chest/upper abdomen feathers. The dark band is also narrower in places and at the bottom it heads into the white coloured feathers of it's shoulder area. The bird may also have a white feather markings on it's right wing but this could be a trick of light.

The circular marking on the throat is usually, I've found, not a good indication at first, in identifying individual birds. As each circular marking is different it is really hard to get these birds to keep still so you can take a photo of their throats. When a bird has just left the nest the juvenile will not have this circular marking yet. They just have a buff coloured throat. As the bird matures the circular marking is formed. However, it will be a good way to tell how old the bird might be by studying how well formed the circular mark is on the bird's throat.

The brown nape coloured feathers also changes with maturity, so this is not a good way to identify individuals of this species. The brown nape coloured feathers eventually spreads down the back of the bird.

Anyway, by studying your own video footage you can clearly identify how many individual birds are in the immediate area using this form of identification alone.

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