Kiskadee nest/widow's fungus

In an earlier post I pointed a finger at the kiskadees (flycatcher family) as being the culprits for spreading a parasitic plant called erva de passarinho (the bird's herb) to other trees around the Bosque reception center. These birds are are guilty also of bringing in another little beauty called fungo de viuva (widow's fungus), which can be seen in the attached image of a kiskadee nest. The fungi are the long white filaments mixed in with a debris of leaves, twigs, grasses and the like. Click in on the thumbnail image for a better view. The tree hosting our little yellow-breasted friends is a Brazil Wood tree (Caesalpinia echinata), which might be the most famous tree in Brazil. It's a relatively rare tree species and we only have two of them at Bosque Santa Lucia. I don't know what attracts the kiskadees to this tree but they've been raising families there for the last four years or so. One batch after another and the proud parents continue to lace their nests with the fungus. What happens is that the fungus will eventually spread to the branches of the tree and if not contained, it'll kill the tree. I wonder if there's something special about the fungus that the birds like, other than the fact that it's easy picking for them. By the way, there are many different species of flycatchers around. My guess is that these little devils are the lesser kiskadees (Pitangus lictor). It's question of time before I get a picture of one!