The Lives and Deaths of Caged Birds: Transatlantic Voyages of Wild Creatures from the Americas to Spain, 1740s–1790s

This essay focuses on New World birds caught up in the eighteenth-century transatlantic trade with other living wild creatures, destined for imperial metropoles. Manuscript sources describing this trade, written by political officials, ships’ captains, doctors, naturalists, animal caretakers, and inspectors who cataloged their arrival to Spanish ports, interacted with the animals, tried to keep them alive aboard the ship, and determined their ability to withstand further transport to their final destinations in Madrid and other cities in Spain. In the process, animals caged aboard ship for several weeks or more developed relationships with one another and with their human caretakers. Their lived experiences show the multiple and complicated ways in which individual captured birds and other creatures helped shape those shipboard environments, disrupting systemic human attempts to construct them as colonial animals who functioned solely as scientific or material objects in empire making.

Minimal effects of latitude on present-day speciation rates in New World birds

The tropics contain far greater numbers of species than temperate regions, suggesting that rates of species formation might differ systematically between tropical and non-tropical areas. We tested this hypothesis by reconstructing the history of speciation in New World (NW) land birds using BAMM, a Bayesian framework for modelling complex evolutionary dynamics on phylogenetic trees. We estimated marginal distributions of present-day speciation rates for each of 2571 species of birds. The present-day rate of speciation varies approximately 30-fold across NW birds, but there is no difference in the rate distributions for tropical and temperate taxa. Using macroevolutionary cohort analysis, we demonstrate that clades with high tropical membership do not produce species more rapidly than temperate clades. For nearly any value of present-day speciation rate, there are far more species in the tropics than the temperate zone. Any effects of latitude on speciation rate are marginal in comparison to the dramatic variation in rates among clades.