sentences:  A 2010 Texas study found that 66% of doves had elevated lead levels.The study noted that birds with lethal concentrations of lead were not found because accidental ingestion of lead shot can kill birds in just two days, and that they are incapacitated before that point, meaning that such birds died before they could be collected by researchers.Climate change is expected to expand their range to the north, but will also threaten populations with increased drought and fire, which destroy habitat, and spring heatwaves which can kill young in the nest.