In the swamps of southern Illinois live a peculiar species of warbler. Prothonotary warblers are yellow as the sun and tend to nest in holes in trees over the water. But, if you put up a cardboard milk carton taped to two aluminum poles they'll prefer to make their home in the nice square condominium. The homes these warblers build also attract another bird, the Brown-headed Cowbird. Inside these nestboxes, cowbirds lay their eggs right next to the warbler eggs and then leave the warbler to raise the cowbird offspring in addition to their own. These cowbirds are vigorous competitors that rapidly outpace the warbler chicks through development and outcompete them for food from parents. The warblers work double-time though and manage to feed the larger brood without losing any of their own. To study the physiological ways in which cowbirds outcompete their adopted siblings, I have been studying how they compete with different numbers of warbler "siblings" for food resources from parents by monitoring their growth daily, mainly in flooded boots.