This is a summary of 2019 osprey research and production assembled and written by Vanessa Greene, an osprey researcher who lives in Hennepin County. It has been edited. This is the 36th year of monitoring the osprey population in the eight-county Twin Cities Metro area. Funding for this project comes via donations.
The first Ospreys of the 2019 season were observed April 6. Reports came from various parts of the metro area. The first signs of incubation were documented April 19.
Last year was a struggle for many ospreys, with a higher failure rate than past years. Although there were 151 occupied nests, eggs were laid in only 140. There were 136 occupied nests in 2018, eggs laid in 125.
At least one chick was confirmed to have fledged successfully or survived to fledging age in 93 of these nests, down from 96 in 2018.
We documented 58 nests which failed, up from 40 in 2018.
The failure rate was 39 percent, a significant increase. In 2018 it was 29 percent, in 2017 28 percent, and in 2016 25 percent.
It was notable that a very large cluster of 20 nest failures occurred in an approximate 10-mile square area surrounding Carver Park and the University of Minnesota Landscape Arboretum, near Victoria, Chanhassen, Chaska and Mound, MN. Most other failures occurred on scattered nests in the metro area.
We do not know the reasons for these failures, but in some cases we suspect a large black fly hatch, after heavy rains, may have affected outcomes. Some adults were observed flying off the nest repeatedly during incubation. Swarms of black flies were seen on some nests with newly hatched chicks which probably succumbed to the constant biting.
The number of chicks known to have fledged successfully or survived to fledging age was 194, close to the 205 fledged in 2018. There were 41 nests with two chicks, 30 nests with three chicks, and 22 nests that produced a single chick.
Mortality rate this year was similar to last year with 17 chicks known to have died or disappeared before fledging, down from 19 last year. Three chicks died post-fledge. Two adults also died, one from a vehicle collision, the other from a possible impact injury after a territorial dispute. It was found dead near another nest on a cell tower with a severely broken wing.
We located 13 new nesting territories. Only four of these new nests successfully fledged chicks. One nest which was occupied by geese for the second year. Of the 151 occupied territories this year, 78 were on osprey nesting platforms, 29 were on cell or radio towers, 22 were on ballfield lights, 18 were on a power pole or transmission tower, two were on other manmade structures and two nests were built in a dead tree.
One of the tree nests produced two chicks which survived to an advanced age, but the nest blew down in a storm and both chicks died.
Productivity of occupied nests successful this year dropped significantly to 62 percent. Previous marks, dating back to 2012, ranged from a high of 77 percent (2012) to a low of 67 percent (2013).
Six male birds monitored this year were 15 or 16 years old. Only two bred successfully. Our oldest female was a banded bird that showed up on a nest this year for the first time, and she was 13 years old, and she bred successfully! We believe she must have been nesting previously in a territory that we don’t know about. There were four 12-year-old females, three of which bred successfully.
We have recorded 2,467 osprey chicks fledged from monitored nests in the eight-county metro area since the inception of this project 36 years ago.
Vanessa Greene, Twin Cities Metro Osprey Watch