Every year from late February to early April over 600,000 Sandhill Cranes migrate on the Platte River valley in Nebraska in order to "fuel up" on their way to the north. Photographing the cranes is a bit challenging as they are very skittish in this area and walk or fly away once a human approaches anywhere within 100 yards. Also, they are more active shortly before sunrise or after sunset when there is little light to photograph moving subjects. I use my 600mm lens on a tripod. Having a full sensor camera would help bump up the ISO. Since my camera has a crop sensor, I hesitate pushing above ISO of 800. Despite these difficulties, it is quite an experience. Air filled with loud rattling sounds and sky obscured by flocks of birds are quite unforgettable.