Severe storms hit the Fort Worth area Thursday morning, bringing hail that killed some of the birds in the city's zoo and forced it to delay opening. A zoo spokesperson tells Fox 4 News that at least two ducks, a pelican, and four or five flamingos were killed when storms hit the zoo around 6:30am. USA Today reports that some of the hail was tennis ball-sized, and it also caused "massive damage" to cars. A ground stop was issued for flights into Dallas/Fort Worth International Airport until 9am local time. (More hail stories.)