This evil little bird makes its living by piercing the base of flowers to steal the nectar which is unfortunate because it drains the flower and frequently prevents regeneration of the nectar the local hummingbirds rely on. Consequently, hummingbirds will harass this bird when they see it. Check out the little hook on the tip of the bill. This one was photographed at Poas Volcano.
And this one at Freddie Fresa's roadside garden near Poas.