There's no "easiest" method in general - depends on preferences (and knowledge of modeling techniques) if they are NURBS or polies. And no surprise that there's no tutorials for building bird legs - it's impossible and unreasonable to create tutorials for everything.
Start by studying thing You are trying to model. Download as much reference images of thing You are going to model, if project is serious then take photos in park or zoo where You can find those birds. Also look zoology encyclopedias and scan some images which suit Your needs. Find a good angles to see foot from top/bottom and side, make them reasonable in size (around 512x512px) and load those as a imagePlanes.
You can start by creating approximate dummy of model to feel a volume of it e.g. create polyCylinder (height 0.7, subdAxis 10), select sequentially faces ## 1, 4, 6, 8 and extrude them for the length of each bird's finger, add subdivisions if necessary, rotate, scale vertices. Template object.
Now model a single finger which You will later duplicate 3 times and scale to fit each finger's size, then join them together.
NURBS or polygons - this decision is up to You.
Basically it depends on what You are going to do with model after:
animate through deformation? : this requires skill of character building, which is beyond any single tutorial;
do closeup renders? : high detalisation - either NURBS or SubD;
fur? : better NURBS.
etc, etc.