This is my Latex code

documentclass[12pt, oneside]{amsart}

%DIF LATEXDIFF DIFFERENCE FILE

%DIF DEL RPI_R1_041.tex      Tue Sep  4 11:13:10 2018

%DIF ADD RPI_R1_041_RA.tex   Fri Sep 21 17:13:32 2018





bibliographystyle{amsplain} 



title{Concentração no ensino superior brasileiro: Maior qualidade vs. maior preço}

author{Alessandro Rivello}

thanks{Projeto de pesquisa para a matéria OI I}



date{Initial draft: 19/03/2019. This version: today}



begin{document}



    maketitle



    setcounter{footnote}{1}



    section{Introdução}

    A presença de empresas privadas na oferta de vagas para o ensino superior brasileiro tem crescido ao longo do tempo. cite{birds1998}



    bibliography{ref}

end{document}

and this is the output that I am getting

he following is my ref.bib file

%% LaTeX2e file `ref.bib'

%% generated by the `filecontents' environment

%% from source `Proj_OI1' on 2019/03/20.

%%

 @misc{birds1998,

  title   ={Sinopse Estatística do Ensino Superior 2017},

  url     ={http://portal.inep.gov.br/basica-censo-escolar-sinopse-sinopse},

  organization={Instituto Nacional de Estudos e Pesquisas Educacionais Anísio Texeira},

  urlaccessdate={19 mar. 2019}

}

And this is the .blg file generated after compiling the Latex code

This is BibTeX, Version 0.99d (TeX Live 2017)

Capacity: max_strings=100000, hash_size=100000, hash_prime=85009

The top-level auxiliary file: Proj_OI1.aux

I found no bibdata command---while reading file Proj_OI1.aux

I found no bibstyle command---while reading file Proj_OI1.aux

You've used 1 entry,

            0 wiz_defined-function locations,

            84 strings with 499 characters,

and the built_in function-call counts, 0 in all, are:

= -- 0

> -- 0

< -- 0

+ -- 0

- -- 0

* -- 0

:= -- 0

add.period$ -- 0

call.type$ -- 0

change.case$ -- 0

chr.to.int$ -- 0

cite$ -- 0

duplicate$ -- 0

empty$ -- 0

format.name$ -- 0

if$ -- 0

int.to.chr$ -- 0

int.to.str$ -- 0

missing$ -- 0

newline$ -- 0

num.names$ -- 0

pop$ -- 0

preamble$ -- 0

purify$ -- 0

quote$ -- 0

skip$ -- 0

stack$ -- 0

substring$ -- 0

swap$ -- 0

text.length$ -- 0

text.prefix$ -- 0

top$ -- 0

type$ -- 0

warning$ -- 0

while$ -- 0

width$ -- 0

write$ -- 0

(There were 2 error messages)

I have being searching for a long time in the Latex stackexchange community and found a lot of related questions, but any of the solutions seems to work for me. What I am doing wrong?

EDIT:

Thank you @daleif. Now I'm getting the correct citation in the text and the list of references is appearing as you can see bellow

But, as you can see the way the list of references are formatted is weird and I'm still getting some error messages while compiling as you can see from the .blg file

This is BibTeX, Version 0.99d (TeX Live 2017)

Capacity: max_strings=100000, hash_size=100000, hash_prime=85009

The top-level auxiliary file: Proj_OI1.aux

The style file: amsplain.bst

Database file #1: ref.bib

Warning--to sort, need author or key in birds1998

You've used 1 entry,

            2213 wiz_defined-function locations,

            502 strings with 4033 characters,

and the built_in function-call counts, 196 in all, are:

= -- 11

> -- 1

< -- 0

+ -- 1

- -- 0

* -- 9

:= -- 25

add.period$ -- 1

call.type$ -- 1

change.case$ -- 3

chr.to.int$ -- 0

cite$ -- 2

duplicate$ -- 11

empty$ -- 27

format.name$ -- 0

if$ -- 41

int.to.chr$ -- 0

int.to.str$ -- 1

missing$ -- 1

newline$ -- 13

num.names$ -- 0

pop$ -- 10

preamble$ -- 1

purify$ -- 2

quote$ -- 0

skip$ -- 8

stack$ -- 0

substring$ -- 5

swap$ -- 1

text.length$ -- 0

text.prefix$ -- 0

top$ -- 0

type$ -- 4

warning$ -- 1

while$ -- 0

width$ -- 2

write$ -- 14

(There was 1 warning)

Any ideas on why this is happening?

Apparently with amsart you have to place bibliographystyle within the document body, not in the preamble. If placed in the preamble the bibstyle is never written to the aux file.

So either place it in the body (I usually have it just above bibliography) or use

AtBeginDocument{

    bibliographystyle{...}

 }