科创中国

Contrary?to?the?nestling?phase,?the?post-fledging?phase?has?been?less?studied?probably?because?it?is?challenging?to?follow?the?chicks?after?they?fledge.?However,?this?phase?is?crucial?to?consider?when?focusing?on?the?life?cycle?of?individuals?because?it?is?associated?with?new?demands:?After?leaving?the?nest,?individuals?have?to?find?their?own?food?and?cope?with?a?new?set?of?previously?unknown?stressors.?In?this?study,?we?aimed?at?better?understanding?how?energetically?demanding?the?post-ftedging?period?is?in?house?sparrows?Passer?domesticus?by?measuring?several?indices?of?a?fledgling's?state?(body?condition,?fat?and?muscle?scores?and?plumage?quality).?If?the?energetic?demands?of?the?post-fledging?period?are?greater?than?those?of?the?adult?life,?we?predicted?that?fledglings?should?be?in?lower?condition?and?should?have?a?plumage?of?lower?quality?relative?to?adults.?Supporting?this?prediction,?the?condition?and?the?plumage?of?fledglings?differed?dramatically?from?those?of?adults.?Interestingly,?this?difference?disappeared?in?autumn.?Overall,?our?results?suggest?that?the?post-fledging?period?is?probably?one?of?the?most?energetically?demanding?of?the?life?cycle?in?this?species.?Supporting?this?idea,?the?resighting?probability?of?fledglings?was?lower?relative?to?adults.?However,?resighting?probability?depends?on?many?factors?(mortality,?dispersal,?habitat?use?and?behaviours)?and?future?studies?are?necessary?to?tease?apart?their?relative?importance?in?determining?resighting?probability?[Current?Zoology?60?(4):?449-459,?2014].

Fear?and?anxiety?may?be?adaptive?responses?to?life-threatening?situations,?and?animals?may?communicate?fear?to?others?vocally.?A?fundamental?understanding?of?fear?inducing?sounds?is?important?for?both?wildlife?conservation?and?management?because?it?helps?us?understand?how?to?design?repellents?and?also?how?(and?why)?animals?may?be?negatively?impacted?by?anthropogenic?sounds.?Nonlinear?phenomena--sounds?produced?by?the?desynchronization?of?vibrations?in?a?sound?production?system-are?commonly?found?in?stress-induced?animal?vocalizations,?such?as?in?alarm?calls,?mobbing?calls,?and?fear?screams.?There?are?several?functional?hypotheses?for?these?nonlinear?phenomena.?One?specific?hypothesis?is?the?unpredictability?hypothesis,?which?suggests?that?because?nonlinear?phenomena?are?more?variable?and?somewhat?unpredictable,?animals?are?less?likely?to?habituate?to?them.?Animals?should,?therefore,?have?a?prolonged?response?to?sounds?with?nonlinear?phenomena?than?sounds?without?them.?Most?of?the?studies?involving?nonlinear?phenomena?have?used?mammalian?subjects?and?conspecific?stimuli.?Our?study?fo-?cused?on?white-crowned?sparrows?(Zonotrichia?leucophrys?ssp.?oriantha)?and?used?synthesized?acoustic?stimuli?to?investigate?behavioral?responses?to?stimuli?with?and?without?nonlinear?phenomena.?We?predicted?that?birds?would?be?less?relaxed?after?hearing?a?stimulus?with?a?nonlinear?component.?We?calculated?the?difference?from?baseline?of?proportion?of?time?spent?in?relaxed?behaviors?and?performed?pair-wise?comparisons?between?a?pure?tone?control?stimulus?and?each?of?three?experimental?stimuli,?including?a?frequency?jump?up,?a?frequency?jump?down,?and?white?noise.?These?comparisons?showed?that?in?the?30q50?s?after?the?playback?experiment,?birds?were?significantly?less?relaxed?after?hearing?noise?or?an?abrupt?frequency?jump?down?an?octave?but?not?an?abrupt?frequency?jump?up?an?octave?or?a?pure?tone.?Nonlinear?phenomena,?therefore,?may?be?generally?arousing?to?animals?and?may?explain?why?these?acoustic?properties?are?commonly?fou