Category: Fighting

Bald Eagles in Utah

Every winter hundreds of Bald Eagles migrate south from Canada and Alaska and winter in Utah.  They do so because of our relatively mild winters and they are able to find sufficient food here.  Typically they begin arriving in November and leave in March when the ice begins to melt.  They can be found in many areas of the state but a large percentage of them winter on the wetlands surrounding the Great Salt Lake where there are a number of bird refuges and other suitable areas to accommodate them.  Adult Bald Eagle in flight Each year I spend many hours at some of the Great Salt Lake wetlands photographing eagles.  What attracts them to some of the refuges is fish – lots of fish,  especially carp.  Carp are a nuissance for wildlife managers because they root in the mud of the shallow impoundments which makes the water cloudy and unable to transmit light to the bottom.  This disrupts the healthy growth of desirable plant species needed by birds so some refuges “poison” the carp, usually in mid-winter, with rotenone – a non-toxic chemical that forms a film on fish gills preventing oxygen transfer from the water to the blood which kills the carp.  Then it’s feast time for the eagles. Bald Eagles and gulls on the ice It’s common to see several hundred Bald Eagles from one spot.  One refuge counted 408 eagles.   I’ve personally seen 150 – 200 birds on several occasions. Immature Bald Eagle with carp This is why they’re here – fish!  Specifically, carp.  Lots of carp…

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Northern Harriers Fight to Survive Harsh Winters

  Typically life is good for the hundreds of Northern Harriers who spend fall and winter in the marshes and prairies surrounding the Great Salt Lake after spending breeding season up north.  Here their diet consists almost exclusively of microtine voles (small rodents resembling mice).  These voles are incredibly abundant and relatively easy prey.  It’s quite unusual to see a harrier even attempt to catch a songbird or anything else for that matter.    Harrier hunting voles near the Great Salt Lake   However the easy life takes a major turn for the worse during unusually harsh winters with intense cold and deep snow packs.  During these times the voles spend most of their time underground eating roots and dried vegetation which means the primary source of food for harriers is suddenly unavailable just when they most need nourishment for warmth.  And since most songbirds (their fall-back food source) have either migrated south or have already succumbed to the many American Kestrels in the region, simple survival for the harriers is suddenly very precarious.  Now, out of desperation,  harriers begin to go for larger prey – ducks and coots for example.     Harrier on a duck kill frozen into the ice They aren’t able to take these prey often and when they do they can’t eat them quickly like they can a vole.  The result is intense aggression – fighting fiercely over food.  Typically I see very little true aggression(other than territorial squabbles) between harriers but all that changes when food becomes scarce.  A relatively large prey item will provide multiple…

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