Saturday, July 11, 2020

Owl Count: It’s Down

This year eighty-nine properties have burrows on site—the lowest number since monitoring began. Submitted photos

This year eighty-nine properties have burrows on site—the lowest number since monitoring began. Submitted photos

It is late in the year for the final count of the Island’s Burrowing Owl population, but it is better late than never. Typically, for the last ten years of monitoring, nesting behavior of this species is seen as early as November and continues through January. First the pairing up of the adult owls; then new burrows may be dug, and old and even burrows that have been abandoned for a two or more seasons will once again be occupied. Next “decoration,” material (ranging from shredded pieces of debris, foil, flowers, coconut husks to feathers and feces of dogs) collected by both owls, but mostly the male, to court the female, camouflage the burrow opening, and cover the smell of the nest and eggs from predators, appears on the burrow mound. After two or three weeks of courting and feeding to absorb enough energy to produce eggs, the female will disappear as she is in the burrow nonstop incubating the clutch of eggs while aggressive protection of the burrow opening by the male begins. After about five weeks of the male perched and standing watch, the female will come out late night or early morning to hunt and feed. Finally, the chicks then emerge, staggered over a few days’ time, in late March or early April. Both adult owls will bring food to the chicks as they learn their surroundings and finally fly and hunt on their own. This series of events has fluctuated a week to three weeks in past years but it never misses a predictable step.

But this season, this series of nesting behavior was not apparent. At first, pairs were observed in average numbers in early December, encouraging hopeful predictions from owl-watchers for a productive nesting season. Then, as the freezing weather came in waves throughout December and January, typical nesting behavior was obviously interrupted and not observed. Many pairs “disappeared” ? most likely hunkered down in their burrow to abate the below-normal temperatures. By the first week of February, no “decoration” was noted at the burrow sites with paired owls and the females were not on eggs. Protection behavior was strong. Finally, by mid April, the nesting behavior was appearing and by May, chicks began to emerge and the count began.

This year there are eighty-nine (89) properties that have burrows onsite; the lowest number since monitoring began in 1999. The burrow(s) are marked with flagging, signs and a perch to protect them from the mowing equipment and other heavy equipment and curious onlookers. The burrows can be inches to about a foot below the soil surface and meander underground an average four to five feet in length to a dead end nesting chamber. Of the 89 sites, forty-three (43) of the burrow sites have owls inhabiting the burrows.  Of the 43 sites, there are twenty-seven (27)

Two chicks with an adult.

Two chicks with an adult.

nesting pairs of Burrowing Owls and sixteen (16) single adults that did not pair up during the nesting season. The resulting forty-six (46) burrow sites that have not been inhabited by owls this season have intact burrows and thus are continued to be protected as it is not unusual for a burrow to be inactive for a few seasons, and then have an owl show up and set up house. Of the 27 pairs that exhibited nesting behavior, three pairs to date have not produced any chicks. These pairs may have lost a clutch in the low temperature periods; the temperatures so low and over long periods of time could have made the eggs nonviable. Most pairs were successful in re-nesting, hence the late season of nesting, while the three non-producing pairs were unsuccessful in producing a second clutch of eggs. This could be due to maturity of the pair, food sources, and timing. The twenty-four (24) pairs have produced a total of 66 chicks that have been observed and documented. The clutch size per pair ranges from one chick to as many as six, but the average represents less than three chicks per pair producing.

This season’s population count is a decrease of approximately 11% from last season in both nesting adult pairs and number of chicks produced which does not bode well for sustainability. The other negative for population increase was that the number of single, or non-paired, adult owls increased by two. The stressors on the population include primarily habitat loss due to construction. Construction impacts are two-fold: the actual construction activity of noise, equipment and activity in close proximity and then the loss of habitat in the addition of development landscape that typically includes the use of pesticide which impacts food sources. Other stressors include past drought cycles that decrease food sources, increase hawk predation, and this past season the obvious low temperature periods.

Though the island will continue to develop and weather cannot be controlled, there are easy ways to help protect and sustain our dwindling Burrowing Owl population. Plant landscapes that are native species or “Florida Friendly” that require less or no pesticide use and attract native insects, amphibians and reptiles as food sources; educate new comers of the Burrowing Owl’s protective status and importance to the ecosystem and community enjoyment; create a “starter burrow” in your yard to attract an owl from properties that have future development impacts; or become a volunteer to monitor and/or maintain the burrow sites on the island.

If interested in encouraging a Burrowing Owl in your yard, are looking for volunteer opportunities or care to observe the owl population on the island using location maps provided at the City of Marco Island, 50 Bald Eagle Drive, please contact Nancy Richie at 239-389-5003, nrichie@cityofmarcoisland.com.

Nancy Richie is the Environmental Specialist for the City of Marco Island.

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