Time structure of behavioral patterns related to feed pecking in chicks

Nonrandom time patterns of pecking acts by 16 chicks were detected using th e software Theme during three videotaped pecking sessions (M, C, and A). At 15 days of age pecking session, M (mash) was recorded when chicks ate a ma sh diet. Pecking session C (change) at 16 or 17 days of age was recorded im mediately after the change of the diet to pellets presented either as regul ar cylinders (P) to eight chicks, or as semiovoid (Po) to eight other chick s. Pecking session A (adapted) was recorded 5 or 6 days after adaptation to P and Po. Successful (consumatory) pecks were 72%, 52%, and 61% of all pec ks for sessions M, C, and A, respectively. The head of the chicks remained in a steady position between two consecutive pecks for a longer period duri ng C (65% of the time) than M and A (54%). During C, the pecking rate was l ess for P (0.54 pecks/s) than for Po (0.79 pecks/s). Two consistent time pa tterns involving four acts frequently observed were: head rotation (or expl oratory peck) double right arrow head in steady position double right arrow consumatory peck double right arrow head in steady position with jaw movem ents. Time intervals within a pattern were stable throughout sessions. Howe ver, the proportion of synchronized (included in a pattern) vs. nonsynchron ized (not included in a pattern) acts decreased immediately after the chang e of feed form (session C). These results suggest that pecking at feed is c omposed of two distinct sets of acts: consistently organized patterns littl e affected by the form of the pecked particles and nonsynchronized acts tha t may be involved in sensory information. (C) 2000 Elsevier Science Inc. Al l rights reserved.