 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 suggested that the direct effects of ALAN were to blame for this sleep disruption .
<clarity>  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 suggested that the direct effects of ALAN were to blame for this sleep disruption .
 However, the researchers found a 50\% reduction in the female Great Tits' total sleep duration during this period in urban centers, and suggested that the direct effects of ALAN were to blame for this sleep disruption .