[ INTRO ].

It's not a great time to be a bird, thanks to things like habitat loss, climate change, and just... people. And last week, a study published in the journal Science, by researchers from institutions across North America, provided shocking evidence of just how bad things have gotten.

It found that since 1970, bird populations in the United States and Canada have dropped by 29%. Which works out to almost three billion birds in less than fifty years. To get to this staggering figure, scientists used multiple bird monitoring survey datasets to study populations from 529 species.

As an additional source of data, they also used weather radar to track migrating species in flight, who may not have shown up on the other ground-based surveys. Although some species increased in abundance, the vast majority dropped in number. For example, those radar surveys indicated a drop in the volume of migrating birds of around 14% since 2007 alone.

And grassland birds were particularly affected. Their numbers have gone down by more than half since 1970, and almost three quarters of grassland species are in decline. And it's not because of really rare birds going extinct. 90% of the total loss in numbers happened in bird families that are pretty common, including warblers, blackbirds and sparrows.

Not all the news was bad. The study also outlined groups that have made a comeback, like waterfowl, whose numbers have increased thanks to wetland restoration. And raptors like the bald eagle, who were helped by endangered species legislation.

But the whole picture is pretty dire. The president of the National Audubon Society has called it a “full-blown crisis”. See, the disappearing birds are an indicator of the health of the environment in general.

North American ecosystems have been so affected by peopl e that they can't support wildlife in the same way they used to. The study didn't pinpoint causes, but the authors suggest that habitat loss -- through agriculture or climate change -- may be at fault. But human population growth could also be bad news for birds, thanks to everything from pet cats to reflective windows.

And that's where we can do something about this bird crisis. Some of the authors of the study also put out a list of things we can do on a personal level. You can, for example, put stickers or screens on windows to stop birds from flying into them.

Or plant more native trees and avoid pesticides to make the outdoors a safe and inviting place for birdlife. Or keep cats indoors -- or even get a catio so they can experience the great outdoors without harming birds. Because here's the thing --.

Whiskers might actually feel more comfortable when she's around you. That's according to a study published this week in the journal Current Biology, which found that cats actually form attachments to people in a similar way to dogs and even human children. Which contradicts cats' reputation for aloofness.

This study used a modified version of a classic psychological test called the Harlow secure base test. In that test, researchers look at how young subjects react to a caregiver coming back after a short time away. The idea is that baby animals -- humans, monkeys, even chicks -- need to stick close to Mom or Dad, at least for a short time, to survive.

If the caregiver leaves, the young one's attachment instincts kick in and they'll feel distressed. When the pair are reunited, they'll greet each other, and that should offer some relief to the infant. /But/ a young animal can't spend its whole time glued to Mom. It also needs to explore and learn about the world.

That's where the secure base part comes in. The caregiver offers a safe, comfortable point to come back to. The test offers a way to stress young animals -- just a little bit -- and then see whether their stress is calmed by the caregiver's return.

Kittens who were securely attached to their human would greet them, but then spend their time between their secure base and exploring their surroundings -- presumably checking in for chin scratchies once in a while. Those that were insecure showed more signs they stayed/ stresse, even after the caregiver came back, like licking their lips or twitching their tails. Out of 79 kittens 70 could be classified using this technique.

And most of them -- around 64 percent -- were secure, which might explain why we think they're aloof if they see us but aren't rubbing up against us as soon as we come home. What was interesting is that these attachments are pretty set once they form. The researchers enrolled some of the kittens in socialization classes with their caregivers.

But, six weeks later, there was no difference in the number of kittens who were classed as secure or insecure. And the breakdown between secure and insecure was pretty much the same when they repeated the experiment with a different group of adult cats. The researchers think that's because cats keep a lot of their baby features into adulthood.

This study shows that having a human caregiver around can actually help cats feel less stressed. And that running and hiding isn't their only option to deal with a scary situation, especially if their human is around. Which means having you around may help your kitty feel safer and more secure.

And that's nice, since it definitely goes the other way too. Thanks for watching this episode of SciShow News! If you're a pin person, we've been doing a cool thing for the past few months.

We've been making a space-themed pin of the month featuring different spacecraft that launched or landed in that month. And they're only available FOR that month. And this month's pin is a viking lander on top of a sparkly retro-rainbow that looks awesome, and it's only available until the end of September, and then we'll be back with a new pin next month!

So if you like celebrating old school space exploration or just like landers that look like they're waving at you, you can check these out over at dftba.com/scishow or probably in the merch self below the video [ outro ].