Background For cavity-nesting birds, the nest entrance plays an important role in preventing predators from accessing nests. Several species of nuthatches use mud to narrow the entrance of cavities. In theory, the smaller the entrance hole size, the more effective it is against predators; however, few studies have tested whether narrowing the entrance hole size can affect the estimation of threat levels from nest predators in cavity-nesting birds. Methods Using dummy experiments, we tested whether Eurasian Nuthatches (Sitta europaea, narrow the entrance hole of cavities) and Cinereous Tits (Parus cinereus, do not narrow the entrance hole, as a control) perform different nest defence behaviours against Common Chipmunks (Tamias sibiricus, small nest predator) and Red Squirrels (Sciurus vulgaris, larger nest predator). Results Both nuthatches and tits exhibited stronger response behaviours (high dummy response scores) against chipmunks than against squirrels. Compared with tits, nuthatches exhibited more aggressive behaviours to chipmunks, but their responses to squirrels were similar. Conclusions Nest defence behaviours of nuthatches to chipmunks differed from tits, and the results suggested that nuthatches might estimate threat levels of nest predators according to their narrowed entrance-hole size.
Objective: There is still no consensus on the time period of wearing protective collar after Anterior Cervical Discectomy and Fusion (ACDF). We aim to investigate the optimal time period of wearing collar after ACDF. Methods: We retrospectively reviewed patients with cervical spondylosis who underwent one or two segment ACDF during January 2016 and December 2017, and included 97 patients who met inclusion and exclusion criteria. Patients were divided into three groups, 1-4 week group, 5-8 week group and 9-12 week group, according to the actual time period of wearing collar after ACDF. We analyzed Japanese Orthopedic Association (JOA) score, Axial Symptom (AS) score and Neck Disability Index (NDI) before surgery and at post-operative 3 months to investigate the optimal time period of wearing collar after ACDF procedure. Results: 1) JOA score: All three groups have a better post-operative JOA score compared with that before surgery (paired t test, p<0.05). There is no significant difference among the three groups with respect to post-operative JOA (ANOVA, p>0.05). 2) AS score: The post-operative AS scores of 1-4 week group and 5-8 week group were significantly better than that before surgery (paired t test, p>0.05). While the post-operative AS score of 9-12 week group was significantly worse than preoperative AS score (paired t test, p<0.05). 3) NDI: All three groups have a better post-operative NDI compared with that before surgery (McNemar test, p<0.05). Of note, in 5-8 weeks group, the percentage of no deficit increased by 45%, and the percentage of mild deficit decreased by 45% accordingly. That percentage is 26% and 31% in 1-4 week group and 9-12 week group, respectively. There was significant difference among these three groups (Fisher’s exact probability test, p<0.05). Conclusion: For cervical spondylosis patients who underwent 1 or 2 segment ACDF, the optimal time period of wearing protective is 5-8 weeks. This time period results in comparable neurological outcome, least risk of axial symptoms, and highest chance of no deficit with neck function.
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