Manual and semi-automatic counting
This involves printing an image of the colony, flock, or its part and then marking off the counted birds or nests. The marked birds / nests are grouped into tens; with larger colonies, supergroups multiplied by 10 are formed into sets of 100 nests / individuals.
Another approach is to use the object counting tool in Adobe Photoshop (Adobe Photoshop PS 2020: Image > Analysis > Count Tool). With this software, the clicks are counted automatically, with the consecutive number being displayed next to the clicked object.
A third method, also using Photoshop software, is to apply a layer to the counted object. This can be an ellipse or a rectangle with no filling. The layer is then duplicated and moved to the next object. When a layer is duplicated, a sequential copy number is assigned to it, so the last layer number plus one (first layer) gives the number of individuals in the count.