 However, the researchers found a 50\% reduction in the female Great Tits' total sleep duration during this period in densely populated urban centers.
<coherence>  However, the researchers found a 50\% reduction in the female Great Tits' total sleep duration during this period in densely populated urban centers.
 The researchers found a 50\% reduction in the female Great Tits' total sleep duration during this period in densely populated urban centers.