Knowledge of cooperative breeding in birds from longitudinal studies is available only for a small proportion of species. This paper reports data from a 12‐year study on the Tibetan Ground Tit Pseudopodoces humilis. On average, 27.2% (range: 13.0–36.1%) of monogamous pairs in each year contained one (85.4%) or more (14.6%) male helpers, 83.7% of which were yearlings staying on natal territories. Most helpers (89.6%) helped once and then bred independently. Adults had male‐biased sex ratios, low annual survival rates (averaging 0.50) and shorter longevities (averaging 1.8 years) compared with low‐altitude avian cooperative breeders, suggesting that mate shortage promotes helping behaviour in this species. Incest occurred rarely (2.1% of pairs), probably because kin recognition occurs through year‐around living in family groups. There was a low level (3.1% of broods) of extra‐pair parentage, which could facilitate the maintenance of cooperative breeding.

To investigate the effects of renin‐angiotensin‐aldosterone system (RAAS) inhibitors on the prognosis in patients with coronavirus disease 2019 (COVID‐19). A meta‐analysis was performed. We systematically searched PubMed, the Cochrane Library, the Web of Science, EMBASE, medRxiv, and bioRxiv database through October 30, 2020. The primary and secondary outcomes were mortality and severe COVID‐19, respectively. We included 25 studies with 22,734 COVID‐19 patients, and we compared the outcomes between patients who did and did not receive angiotensin‐converting enzyme inhibitors/angiotensin receptor blockers (ACEIs/ARBs). The use of ACEIs/ARBs was not associated with higher risks of severe disease (odds ratio [OR] = 0.89; 95% confidence interval [CI]: 0.63, 1.15; I 2 = 38.55%), mechanical ventilation (OR = 0.89; 95% CI: 0.61, 1.16; I 2 = 3.19%), dialysis (OR = 1.24; 95% CI: 0.09, 2.39; I 2 = 0.00%), or the length of hospital stay (SMD = 0.05; 95% CI: −0.16, 0.26; I 2 = 84.43%) in COVID‐19 patients. The effect estimates showed an overall protective effect of ACEIs/ARBs against mortality (OR = 0.65; 95% CI: 0.46, 0.85; I 2 = 73.37%), severity/mortality (OR = 0.69; 95% CI: 0.43, 0.95; I 2 = 22.90%), transfer to the intensive care unit among COVID‐19 patients with hypertension (OR = 0.36, 95% CI: 0.19, 0.53, I 2 = 0.00%), hospitalization (OR = 0.79; 95% CI: 0.60, 0.98; I 2 = 0.00%), and acute respiratory distress syndrome (OR = 0.71; 95% CI: 0.46, 0.95; I 2 = 0.00%). The use of RAAS inhibitor was not associated with increased mortality or disease severity in COVID‐19 patients. This study supports the current guidelines that discourage the discontinuation of RAAS inhibitors in COVID‐19 patients.

The way in which breeders respond to helping, in terms of either offspring production or their own survival, may reflect the adaptive aspects of a cooperative breeding system. We explore this issue using a 5-year study of the Ground Tit Pseudopodoces humilis, a facultative cooperative breeder in which 47% of socially monogamous pairs have between one and four close male relatives as helpers. We found that helped nests did not fledge more or heavier nestlings than unhelped nests, and male young from helped and unhelped nests were equally likely to recruit into the local breeding population. However, helped parents of both sexes had a higher probability of survival to the following year than did unhelped parents. These findings suggest that Ground Tit parents with helpers trade current reproduction for personal survival and future reproduction, a strategy favoured by selection to cope with harsh, unpredictable environments such as the Tibetan Plateau.

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Among avian cooperative breeders, help in raising offspring is usually provided by males or by both sexes. Sex bias in helping should evolve in response to sex-specific ecological constraints on independent reproduction, with mate shortage for males and breeding vacancy shortage for each sex. Given that male-biased adult sex ratios are prevalent among birds, we predict that maleonly helping mainly occurs in temperate species where fast population turnovers deriving from low adult annual survival allow all adult females to hold breeding vacancies, whereas some males overflow as helpers, and bothsex helping in tropical species where saturated habitats prevent not only males, but also females from breeding themselves. As expected, we found that across species, adult survival increased towards tropical zones and warmer climates, and higher adult survival tended to be associated with both-sex helping. Furthermore, sex bias in helping was predicted by latitude and ambient temperature. Our findings of demographic response of species to climate as a potential determinant of bias in helper sex uncover how ecological constraints operate to limit independent reproduction in sex-specific ways.