Very nice shot, Shalu. I shot a number of birds just like the two you posted, and did my darnedest to figure out what kind of warbler they are. With all the photos I looked and compared, I kinda felt that they were orange-crowned warblers. The orange crown is rarely seen. It's only visible when the bird is excited and raises its head feathers.
My main reference is Sibley, 'Field Guide To Birds of Western North America. But the photo in this book are deceiving. They do not show the bird's yellowish olive color that we are seeing. Check out the link above, and see what you think. Another possibility is the Yellow Warbler. See the link below.