January 7, 2014 - We began to monitor for signs of migration in December, 2013, and on this January date catch our first Northern red-legged frogs. We intend to intercept frogs coming down out of the forest on their way to the riverside wetland, the dramatically growing traffic on the four lane highway -- as well as the two roads and two rail tracks also between the forest and wetland -- make their journey increasingly perilous. After ferrying frogs to the wetland we realize we also have to get the frogs back to the forest. Our monitoring for migration, and frog catching, lasts into April.
The totals for that first year: 580 frogs down to the wetland; 226 males, and 346 females, with 8 of unknown gender. 572 frogs up to the forest; 162 males and 380 females, with 30 of unknown gender, perhaps including juveniles who spend their first year in the wetland. (Discrepancies may be attributable to frogs that make it on their own.)
This winter the migration began three weeks earlier than the previous year, on December 21, 2014, conditions apparently pleasing to the frogs.
The totals for this second year: 695 frogs headed down to the wetland; 232 males, and 463 females. 750 frogs heading up to the forest; 194 males, 523 females, with 33 of unknown gender, likely including juveniles.
Once again the frogs fooled us, with a small migration once again taking place three weeks earlier than the previous year, on December 8, 2015, and a large migration of 380 frogs the very next night. The migrations petered out in March, as they had the previous year, the length of the breeding season fairly constant.
The totals for this third year were 688 frogs going down to the wetland, and 1040 frogs heading back to the forest (more complete figures are coming). This large discrepancy is as yet unexplained.
The current winter's migrations began on November 14, an anamoly perhaps explained by the "super moon" that night, as conditions remained favorable for migration for several subsequent nights with no migration apparent. A cold winter has kept the frogs at bay, with no migrations well into January.
Totals so far are 831 frogs going down and 188 going up, these figures obviously very preliminary.