The only similar species over most of the Curlew's range is the Whimbrel. This is smaller, and has a shorter bill with a kink rather than a smooth curve.
This species feeds by probing soft mud for small invertebrates. This can be seen in the photo. There is a clearly defined mark on the beak which is , in fact mud at the depth it is feeding in the soft mud.It will will also pick small crabs and earthworms off the surface if the opportunity arises.
The nest is a bare scrape on taiga, meadow or similar habitat. 3-6 eggs are laid, and incubated for about a month to hatching.