Molothrus ater 8 bird 6 Aves 4 Brood parasitism 4 Cowbird 4 Molothrus 4 Turdus migratorius 4 nonhuman 4 parasitism 4 3D printing 2 Agelaius 2 Agelaius phoeniceus 2 American robin 2 Animalia 2 Article 2 Artificial egg 2 Begging 2 Dendroica petechia 2 Egg rejection 2 Experimental techniques 2 Mimus saturninus 2 Molothrus bonariensis 2 North America 2 South America 2 Supernormal stimulus 2 Troglodytes 2 Troglodytes aedon 2 adaptation 2 animal behavior 2 animal experiment 2