Reserva Laguna Nimez is a nature reserve right in downtown El Calafate.

Around 80 species of birds call it home but it depends on the season as many are migratory. Spring and summer are the best seasons for bird watching here.

There’s a self-guided trail with markers explaining the ecosystems and wildlife that live here. It takes an hour and a half (more if you’d like to take advantage of the special access to Lago Argentino’s beach). 
This is an easy and great activity for an arrival or departure day or to tack onto the end of a day at the glacier.

Hours:

• Open 7 days a week

• Summer: 9:30 am - 7:30 pm

• Winter: 10 am - 6 pm

Check current rates here which differ for international visitors, Argentines, students, and retirees. Under 18 is free. Discounts are only for Argentine retirees but for students I believe residence doesn't matter.