Alarm over a species’ de­cline

The bur­row­ing owl’s num­bers have fallen sharply in its Im­pe­rial Val­ley strong­hold.

Los Angeles Times - - California - Louis Sa­h­a­gun­h­a­

An alarm­ing de­cline in the num­ber of bur­row­ing owls in the Im­pe­rial Val­ley — a South­ern Cal­i­for­nia agri­cul­tural area that had been con­sid­ered a strong­hold for the species — has prompted calls for an im­me­di­ate in­quiry by state wildlife au­thor­i­ties.

Sur­veys by the Im­pe­rial Ir­ri­ga­tion District show the bur­row­ing owl pop­u­la­tion has dropped from about 5,600 pairs in the early 1990s to 4,879 pairs in 2007 and 3,557 pairs in 2008.

“We’ve seen a 27% drop in one year alone,” said Jeff Miller, a con­ser­va­tion ad­vo­cate for the Cen­ter for Bi­o­log­i­cal Di­ver­sity. “If there is a sim­i­lar drop next year, this bird could dis­ap­pear in Cal­i­for­nia.”

Statewide, the owl has been de­creas­ing be­cause of habi­tat loss through ur­ban devel­op­ment, elim­i­na­tion of ro­dents it feeds on, pes­ti­cides, pre­da­tion by do­mes­tic an­i­mals, ve­hi­cle strikes, con­tact with wind tur­bines and shoot­ing.

Bur­row­ing owls are be­tween 9 and 11inches tall and make their nests in holes and tun­nels once in­hab­ited by ground squir­rels.

Most of Cal­i­for­nia’s re­main­ing breed­ing pairs are con­cen­trated in the Im­pe­rial Val­ley, an area that con­sti­tutes roughly 2.5% of the state’s land, Miller said. “We still don’t know ex­actly what is caus­ing the de­clines in the Im­pe­rial Val­ley,” he said, “but loss of suit­able for­ag­ing ar­eas from fal­low­ing of agri­cul­tural fields due to wa­ter trans­fers and ground squir­rel erad­i­ca­tion pro­grams may play a role.”

In 2003, the Cen­ter for Bi­o­log­i­cal Di­ver­sity and other en­vi­ron­men­tal groups, in­clud­ing De­fend­ers of Wildlife and the San Bernardino Val­ley Audubon So­ci­ety, filed a pe­ti­tion un­der the En­dan­gered Species Act to pro­tect the bur­row­ing owl.

The Cal­i­for­nia Fish and Game Com­mis­sion re­jected that pe­ti­tion, in part be­cause it be­lieved the bird con­tin­ued to thrive in the Im­pe­rial Val­ley and along the lower Colorado River.

“That ar­gu­ment was flawed to be­gin with,” Miller said. “It’s time to re­visit the is­sue of state-threat­ened pro­tec­tions for the bur­row­ing owl.”

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