If you're wondering whether endangered.org is a legitimate nonprofit, the evidence points clearly to yes. The Endangered Species Coalition has maintained this domain for 27 years, publishes its team, mission, and contact info, and is not flagged by any security watchlists. It's a real advocacy organization with a long track record.
That said, there are a couple of things worth noting. The site loads 29 external scripts — more than expected for a simple nonprofit homepage — which could affect performance or privacy. More importantly, it's missing a privacy policy and terms of service. For a site that accepts donations, that's a gap most legitimate nonprofits fill. It doesn't make endangered.org a scam, but it is something to consider before entering personal or payment information.
Overall, endangered.org reviews from a trust perspective are positive. The organization is who it says it is. Just be aware that the lack of formal legal pages means you're relying on their reputation rather than contractual protections.