鸟类体型变大 是气候变迁还是全球变暖所致
<p><span word="Birds">Birds</span> <span word="are">are</span> <span word="getting">getting</span> <span word="bigger">bigger</span> <span word="to">to</span> <span word="survive">survive</span> <span word="harsh">harsh</span> <span word="storms">storms</span> <span word="related">related</span> <span word="to">to</span> <span word="climate">climate</span> <span word="change">change</span>, <span word="scientists">scientists</span> <span word="have">have</span> <span word="suggested">suggested</span>.</p><p><span word="A">A</span> <span word="study">study</span> <span word="spanning">spanning</span> 40 <span word="years">years</span> <span word="found">found</span> <span word="that">that</span> <span word="birds">birds</span> <span word="in">in</span> <span word="central">central</span> <span word="California">California</span> <span word="are">are</span> <span word="significantly">significantly</span> <span word="larger">larger</span> <span word="than">than</span> <span word="they">they</span> <span word="were">were</span> 25 <span word="to">to</span> 40 <span word="years">years</span> <span word="ago">ago</span>.</p><p><span word="Robins">Robins</span>, <span word="for">for</span> <span word="example">example</span>, <span word="have">have</span> <span word="increased">increased</span> <span word="by">by</span> <span word="an">an</span> <span word="eighth">eighth</span> <span word="of">of</span> <span word="an">an</span> <span word="inch">inch</span> <span word="in">in</span> <span word="wing">wing</span> <span word="length">length</span> <span word="and">and</span> <span word="about">about</span> 0.2 <span word="ounces">ounces</span> <span word="in">in</span> <span word="weight">weight</span> <span word="since">since</span> <span word="the">the</span> 1980<span word="s">s</span>.</p><p><span word="On">On</span> <span word="average">average</span>, <span word="birds">birds</span> <span word="in">in</span> <span word="central">central</span> <span word="California">California</span> <span word="have">have</span> <span word="bulked">bulked</span> <span word="up">up</span> <span word="between">between</span> <span word="two">two</span> <span word="and">and</span> <span word="five">five</span> <span word="per">per</span> <span word="cent">cent</span> <span word="in">in</span> <span word="body">body</span> <span word="weight">weight</span> <span word="and">and</span> <span word="wingspan">wingspan</span>.</p><p><span word="Researchers">Researchers</span> <span word="suggested">suggested</span> <span word="this">this</span> <span word="increase">increase</span> <span word="in">in</span> <span word="body">body</span> <span word="weight">weight</span> <span word="is">is</span> <span word="to">to</span> <span word="protect">protect</span> <span word="the">the</span> <span word="birds">birds</span> <span word="during">during</span> <span word="increasingly">increasingly</span> <span word="erratic">erratic</span> <span word="weather">weather</span> <span word="as">as</span> <span word="global">global</span> <span word="temperatures">temperatures</span> <span word="rise">rise</span>.</p><p><span word="The">The</span> <span word="findings">findings</span>, <span word="published">published</span> <span word="in">in</span> <span word="Global">Global</span> <span word="Change">Change</span> <span word="Biology">Biology</span>, <span word="are">are</span> <span word="at">at</span> <span word="odds">odds</span> <span word="with">with</span> <span word="previous">previous</span> <span word="research">research</span>.</p><p><span word="One">One</span> <span word="ecological">ecological</span> <span word="benchmark">benchmark</span>, <span word="Bergmann">Bergmann</span>’<span word="s">s</span> <span word="rule">rule</span>, <span word="states">states</span> <span word="that">that</span> <span word="birds">birds</span> <span word="and">and</span> <span word="mammals">mammals</span> <span word="tend">tend</span> <span word="to">to</span> <span word="be">be</span> <span word="larger">larger</span> <span word="at">at</span> <span word="higher">higher</span> <span word="latitudes">latitudes</span>, <span word="perhaps">perhaps</span> <span word="to">to</span> <span word="conserve">conserve</span> <span word="body">body</span> <span word="heat">heat</span>.</p><p><span word="In">In</span> <span word="keeping">keeping</span> <span word="with">with</span> <span word="this">this</span> <span word="reasoning">reasoning</span>, <span word="birds">birds</span> <span word="and">and</span> <span word="mammals">mammals</span> <span word="would">would</span> <span word="get">get</span> <span word="smaller">smaller</span> <span word="to">to</span> <span word="adapt">adapt</span> <span word="to">to</span> <span word="rising">rising</span> <span word="global">global</span> <span word="temperatures">temperatures</span>.</p><p><span word="The">The</span> <span word="researchers">researchers</span>, <span word="led">led</span> <span word="by">by</span> <span word="San">San</span> <span word="Francisco">Francisco</span> <span word="State">State</span> <span word="University">University</span> <span word="graduate">graduate</span> <span word="student">student</span> <span word="Rae">Rae</span> <span word="Goodman">Goodman</span>, <span word="wrote">wrote</span>: “<span word="Previous">Previous</span> <span word="studies">studies</span> <span word="from">from</span> <span word="other">other</span> <span word="regions">regions</span> <span word="of">of</span> <span word="the">the</span> <span word="world">world</span> <span word="have">have</span> <span word="documented">documented</span> <span word="decreases">decreases</span> <span word="in">in</span> <span word="avian">avian</span> <span word="body">body</span> <span word="size">size</span> <span word="and">and</span> <span word="have">have</span> <span word="used">used</span> <span word="Bergmann">Bergmann</span>'<span word="s">s</span> <span word="rule">rule</span> <span word="and">and</span> <span word="increases">increases</span> <span word="in">in</span> <span word="mean">mean</span> <span word="temperature">temperature</span> <span word="to">to</span> <span word="explain">explain</span> <span word="these">these</span> <span word="shifts">shifts</span>."</p><p>“<span word="Because">Because</span> <span word="our">our</span> <span word="results">results</span> <span word="do">do</span> <span word="not">not</span> <span word="support">support</span> <span word="this">this</span> <span word="pattern">pattern</span>, <span word="we">we</span> <span word="propose">propose</span> <span word="that">that</span> <span word="rather">rather</span> <span word="than">than</span> <span word="responding">responding</span> <span word="to">to</span> <span word="increasing">increasing</span> <span word="mean">mean</span> <span word="temperatures">temperatures</span>, <span word="avian">avian</span> <span word="body">body</span> <span word="size">size</span> <span word="in">in</span> <span word="central">central</span> <span word="California">California</span> <span word="may">may</span> <span word="be">be</span> <span word="influenced">influenced</span> <span word="by">by</span> <span word="changing">changing</span> <span word="climatic">climatic</span> <span word="variability">variability</span>.”</p>
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