As part of our zoology curriculum we studied the classification of Birds. One of the largest Order (A tier of classification) is "Passeriformes". The passeriformes or perching birds are known for their characteristic toe arrangement which is suitable for perching on various surfaces. They have 3 Toes in front and one at the back which helps them to hold grip over the perch. This type of arrangement can be seen in wide range of birds. There is one other type of arrangement where 2 toes are present each on front and rear side, which is helpful in vertical bark climbs etc.
Recently we got to observe a pale billed flowerpecker collecting spider web fibres for nesting. It was so engrossed in the web collection that it literally went upside down pulling the threads. It was a beautiful sight to observe this little one trying to pull off those sticky threads and wind them. He was trying with all his might, all the while being perched on branches 5-10mm thick. I tried capturing its grip over the perch, displaying the importance of the toe arrangement. Sharing here with some images from the series.
Note the toe arrangements and grip over the branch.