Drastic drop in Martins this year

[robndebby]

We have had a big drop in the amount of Martins that showed up this year. It has been about 25 years and we always had about 32 pair with anywhere from 155 to 172 babies, and four unused gourds. This year we have 52 babies, 11 eggs we are not sure are going to hatch, and 11 empty gourds. Has anyone had this happen or knows if something in nature this year caused a change in the amount of birds?