ML643460501

观察细节

Conservative estimate of the group of Swifts which went to roost in one chimney on the south end of the Burgess Norton factory. First in at 6:14p. Most went in between 6:33-6:36p with a continuous rapid funneling in. Circling flying activity before going to roost was uncharacteristically chaotic versus the usual circling together and reverse circling. Surprised to see this large number still roosting this late into October. Counted by 10-20 as went into roost up to 100, marked each 100 and then multiplied the finally tally of marks by 100. Very experienced with counting large groups of roosting CHSW, been doing this for 14 years.