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CREAM-SKIMMER VERSUS CRUMB-PICKERS ( Coexistence based on patch use )

CREAM-SKIMMER VERSUS CRUMB-PICKERS ( Coexistence based on patch use ). Habitat. Patch. Food item. Its not necessarily how quickly you eat, but what you leave behind. Cream-skimmer are poor exploiters – leave much food behind

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CREAM-SKIMMER VERSUS CRUMB-PICKERS ( Coexistence based on patch use )

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  1. CREAM-SKIMMER VERSUS CRUMB-PICKERS (Coexistence based on patch use) Habitat Patch Food item Its not necessarily how quickly you eat, but what you leave behind

  2. Cream-skimmer are poor exploiters – leave much food behind Crumb-pickers are good exploiters that leave very little food behind

  3. Golden-winged Sunbird Variable Sunbird Malachite Sunbird

  4. Variable Golden-winged Malachite mint flower 62% nectar removal 82% 90% Bill: 20mm 33mm 30mm Time: 2.8 sec 1.8 sec 1.3 sec Rate: 1.1 l/s 2.4l/s 3.6l/s (Gill and Wolf 1978)

  5. Variable Malachite Can the Malachite Sunbird invade a world of Variable Sunbirds?

  6. Variable Malachite Can the Malachite Sunbird invade a world of Variable Sunbirds?

  7. Variable Malachite Can the Variable Sunbird invade a world of Malachite Sunbirds?

  8. Variable Malachite Can the Variable Sunbird invade a world of Malachite Sunbirds?

  9. So, Crumb-pickers always beat out Cream-skimmers (all else equal). How can we get CS and CP to coexist??

  10. So, Crumb-pickers always beat out Cream-skimmers (all else equal). How can we get CS and CP to coexist?? First, recognize that patches can come in 2 forms… Rich Patches and Poor Patches (and rich patches become poor patches as food is depleted) Because Cream-skimmers always lose at the poor patch, to have an advantage, they must be the first (on average) to reach a rich patch. HOW??

  11. So, Crumb-pickers always beat out Cream-skimmers (all else equal). How can we get CS and CP to coexist?? First, recognize that patches can come in 2 forms… Rich Patches and Poor Patches (and rich patches become poor patches as food is depleted) Because Cream-skimmers always lose at the poor patch, to have an advantage, they must be the first (on average) to reach a rich patch. • Be fast!!! • Be DESPOTIC – and just beat the snot out of CPs

  12. Coexisting gerbils in the Negev Desert, Israel Gerbillus allenbyii Allenby’s Gerbil ~20 g Gerbillus pyramidum Egyptian Gerbil Both eat seeds of desert annuals Both are nocturnal ~40 g

  13. Coexisting gerbils in the Negev Desert, Israel Gerbillus allenbyii No matter where or when you put a food patch (composed of seed and sand) out Gaalways forages it down to a lower resource abundance than Gp Gp = cream skimmer Ga = crumb picker Gerbillus pyramidum

  14. Coexisting gerbils in the Negev Desert, Israel Gerbillus allenbyii Gp Gerbillus pyramidum Ga Grams of seeds left behind open under bush

  15. But gerbils partition the night. G. pyramidum forages early in the night (rich patches), whereas G. allenbyii forages later (poor patches). Control Gp removed Percentage of trays visited by G. allenbyii Time (hrs after sunset) But this activity pattern disappears when G. pyramidum is removed (Kotler et al. 1996)

  16. Gp come out Gp back to burrow Ga come out Let’s kick some Allenbyii butt ARE THEY GONE YET?? Food patch

  17. The Cream-skimmer, G. pyramidum, monopolizes access to high quality patches by interference competition, and pushes the smaller G. allenbyii aside. Ultimately, the whole system works b/c much of the inner Negev Desert experiences strong nightly winds that redistribute seeds on a nightly basis. On the coast, where winds are not strong, G. pyramidum does not occur.

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