1983 R.L. Mumme 5 M. formicivorus Plague 1 May Checked the hole 1015, 7 eggs now, clutch is probably complete, 4-3 in favor of 2496! 15 May Disappointing developments here, at 0900 I found the nest has failed: 6 nestlings (from all but egg 4) found dead in the nest. Swarming around the nest hole and over the dead nestling were those nasty, formic acid "oak ants", the same species that may have contributed to the demise of the 1980 nestlings I last checked the hole on 12 May, when 4 nestling egg 6 (pipped) + 5 were present. It looks like the Plague nestlings have been dead only for a day or so, and one of the nestlings had grown quite a bit from since I last saw him, so I put the failure date at 14 May Plague still has some acorns (not many) so I don't know what to attribute the deaths to: ① Starvation, the ants, ② ants, or ③ ants, abandonment - starvation. Hard to say for sure, but I suspect ③. 21 May Routine granary census. Not much interest in nesting, as far as I can tell. 3521 made a quick visit to the hole, but that was it (unless they are interested in the cayre holes 27 May After seeing birds in the Plague nest hole, at 1530 I climb up and find [illegible], which I number (I'll measure them later). Only interesting thing is that a 2 dive bombed me while I was checking the nest. Never brushed my head! Late nest, no further chance of re-nesting, high defense rate